Class Scanner

java.lang.Object
- java.util.Scanner

All Implemented Interfaces:: Closeable, AutoCloseable, Iterator<String>

public final class Scanner
extends Object
implements Iterator<String>, Closeable

A simple text scanner which can parse primitive types and strings using regular expressions.

A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace. The resulting tokens may then be converted into values of different types using the various next methods.

For example, this code allows a user to read a number from System.in:

Scanner sc = new Scanner(System.in);
int i = sc.nextInt();

As another example, this code allows long types to be assigned from entries in a file myNumbers:

Scanner sc = new Scanner(new File("myNumbers"));
while (sc.hasNextLong()) {
    long aLong = sc.nextLong();
}

The scanner can also use delimiters other than whitespace. This example reads several items in from a string:

String input = "1 fish 2 fish red fish blue fish";
Scanner s = new Scanner(input).useDelimiter("\\s*fish\\s*");
System.out.println(s.nextInt());
System.out.println(s.nextInt());
System.out.println(s.next());
System.out.println(s.next());
s.close();

prints the following output:

1
2
red
blue

The same output can be generated with this code, which uses a regular expression to parse all four tokens at once:

String input = "1 fish 2 fish red fish blue fish";
Scanner s = new Scanner(input);
s.findInLine("(\\d+) fish (\\d+) fish (\\w+) fish (\\w+)");
MatchResult result = s.match();
for (int i=1; i<=result.groupCount(); i++)
    System.out.println(result.group(i));
s.close();

The default whitespace delimiter used by a scanner is as recognized by Character.isWhitespace(). The reset() method will reset the value of the scanner's delimiter to the default whitespace delimiter regardless of whether it was previously changed.

A scanning operation may block waiting for input.

The next() and hasNext() methods and their companion methods (such as nextInt() and hasNextInt()) first skip any input that matches the delimiter pattern, and then attempt to return the next token. Both hasNext() and next() methods may block waiting for further input. Whether a hasNext() method blocks has no connection to whether or not its associated next() method will block. The tokens() method may also block waiting for input.

The findInLine(), findWithinHorizon(), skip(), and findAll() methods operate independently of the delimiter pattern. These methods will attempt to match the specified pattern with no regard to delimiters in the input and thus can be used in special circumstances where delimiters are not relevant. These methods may block waiting for more input.

When a scanner throws an InputMismatchException, the scanner will not pass the token that caused the exception, so that it may be retrieved or skipped via some other method.

Depending upon the type of delimiting pattern, empty tokens may be returned. For example, the pattern "\\s+" will return no empty tokens since it matches multiple instances of the delimiter. The delimiting pattern "\\s" could return empty tokens since it only passes one space at a time.

A scanner can read text from any object which implements the Readable interface. If an invocation of the underlying readable's read() method throws an IOException then the scanner assumes that the end of the input has been reached. The most recent IOException thrown by the underlying readable can be retrieved via the ioException() method.

When a Scanner is closed, it will close its input source if the source implements the Closeable interface.

A Scanner is not safe for multithreaded use without external synchronization.

Unless otherwise mentioned, passing a null parameter into any method of a Scanner will cause a NullPointerException to be thrown.

A scanner will default to interpreting numbers as decimal unless a different radix has been set by using the useRadix(int) method. The reset() method will reset the value of the scanner's radix to 10 regardless of whether it was previously changed.

Localized numbers

An instance of this class is capable of scanning numbers in the standard formats as well as in the formats of the scanner's locale. A scanner's initial locale is the value returned by the Locale.getDefault(Locale.Category.FORMAT) method; it may be changed via the useLocale() method. The reset() method will reset the value of the scanner's locale to the initial locale regardless of whether it was previously changed.

The localized formats are defined in terms of the following parameters, which for a particular locale are taken from that locale's DecimalFormat object, df, and its and DecimalFormatSymbols object, dfs.

LocalGroupSeparator: The character used to separate thousands groups, i.e., dfs.getGroupingSeparator()
LocalDecimalSeparator: The character used for the decimal point, i.e., dfs.getDecimalSeparator()
LocalPositivePrefix: The string that appears before a positive number (may be empty), i.e., df.getPositivePrefix()
LocalPositiveSuffix: The string that appears after a positive number (may be empty), i.e., df.getPositiveSuffix()
LocalNegativePrefix: The string that appears before a negative number (may be empty), i.e., df.getNegativePrefix()
LocalNegativeSuffix: The string that appears after a negative number (may be empty), i.e., df.getNegativeSuffix()
LocalNaN: The string that represents not-a-number for floating-point values, i.e., dfs.getNaN()
LocalInfinity: The string that represents infinity for floating-point values, i.e., dfs.getInfinity()

Number syntax

The strings that can be parsed as numbers by an instance of this class are specified in terms of the following regular-expression grammar, where Rmax is the highest digit in the radix being used (for example, Rmax is 9 in base 10).

NonAsciiDigit:: A non-ASCII character c for which Character.isDigit(c) returns true
Non0Digit:: [1-Rmax] | NonASCIIDigit
Digit:: [0-Rmax] | NonASCIIDigit
GroupedNumeral:: ( Non0Digit Digit?Digit?; ( LocalGroupSeparator Digit Digit Digit )+ )
Numeral:: ( ( Digit+ ) |GroupedNumeral )
Integer:: ( [-+]? ( Numeral) ); | LocalPositivePrefix Numeral LocalPositiveSuffix; | LocalNegativePrefix Numeral LocalNegativeSuffix
DecimalNumeral:: Numeral; | Numeral LocalDecimalSeparator Digit*; | LocalDecimalSeparator Digit+
Exponent:: ( [eE] [+-]? Digit+ )
Decimal:: ( [-+]? DecimalNumeral Exponent? ); | LocalPositivePrefix DecimalNumeral LocalPositiveSuffix Exponent?; | LocalNegativePrefix DecimalNumeral LocalNegativeSuffix Exponent?
HexFloat:: [-+]? 0[xX][0-9a-fA-F]*\.[0-9a-fA-F]+ ([pP][-+]?[0-9]+)?
NonNumber:: NaN |LocalNan| Infinity |LocalInfinity
SignedNonNumber:: ( [-+]? NonNumber ); | LocalPositivePrefix NonNumber LocalPositiveSuffix; | LocalNegativePrefix NonNumber LocalNegativeSuffix
Float:: Decimal | HexFloat | SignedNonNumber

Whitespace is not significant in the above regular expressions.

Since:: 1.5

Constructors

Constructor	Description
`Scanner(File source)`	Constructs a new `Scanner` that produces values scanned from the specified file.
`Scanner(File source, String charsetName)`	Constructs a new `Scanner` that produces values scanned from the specified file.
`Scanner(File source, Charset charset)`	Constructs a new `Scanner` that produces values scanned from the specified file.
`Scanner(InputStream source)`	Constructs a new `Scanner` that produces values scanned from the specified input stream.
`Scanner(InputStream source, String charsetName)`	Constructs a new `Scanner` that produces values scanned from the specified input stream.
`Scanner(InputStream source, Charset charset)`	Constructs a new `Scanner` that produces values scanned from the specified input stream.
`Scanner(Readable source)`	Constructs a new `Scanner` that produces values scanned from the specified source.
`Scanner(String source)`	Constructs a new `Scanner` that produces values scanned from the specified string.
`Scanner(ReadableByteChannel source)`	Constructs a new `Scanner` that produces values scanned from the specified channel.
`Scanner(ReadableByteChannel source, String charsetName)`	Constructs a new `Scanner` that produces values scanned from the specified channel.
`Scanner(ReadableByteChannel source, Charset charset)`	Constructs a new `Scanner` that produces values scanned from the specified channel.
`Scanner(Path source)`	Constructs a new `Scanner` that produces values scanned from the specified file.
`Scanner(Path source, String charsetName)`	Constructs a new `Scanner` that produces values scanned from the specified file.
`Scanner(Path source, Charset charset)`	Constructs a new `Scanner` that produces values scanned from the specified file.

Methods

Modifier and Type	Method	Description
`void`	`close()`	Closes this scanner.
`Pattern`	`delimiter()`	Returns the `Pattern` this `Scanner` is currently using to match delimiters.
`Stream<MatchResult>`	`findAll(String patString)`	Returns a stream of match results that match the provided pattern string.
`Stream<MatchResult>`	`findAll(Pattern pattern)`	Returns a stream of match results from this scanner.
`String`	`findInLine(String pattern)`	Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.
`String`	`findInLine(Pattern pattern)`	Attempts to find the next occurrence of the specified pattern ignoring delimiters.
`String`	`findWithinHorizon(String pattern, int horizon)`	Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.
`String`	`findWithinHorizon(Pattern pattern, int horizon)`	Attempts to find the next occurrence of the specified pattern.
`boolean`	`hasNext()`	Returns true if this scanner has another token in its input.
`boolean`	`hasNext(String pattern)`	Returns true if the next token matches the pattern constructed from the specified string.
`boolean`	`hasNext(Pattern pattern)`	Returns true if the next complete token matches the specified pattern.
`boolean`	`hasNextBigDecimal()`	Returns true if the next token in this scanner's input can be interpreted as a `BigDecimal` using the `nextBigDecimal()` method.
`boolean`	`hasNextBigInteger()`	Returns true if the next token in this scanner's input can be interpreted as a `BigInteger` in the default radix using the `nextBigInteger()` method.
`boolean`	`hasNextBigInteger(int radix)`	Returns true if the next token in this scanner's input can be interpreted as a `BigInteger` in the specified radix using the `nextBigInteger()` method.
`boolean`	`hasNextBoolean()`	Returns true if the next token in this scanner's input can be interpreted as a boolean value using a case insensitive pattern created from the string "true\|false".
`boolean`	`hasNextByte()`	Returns true if the next token in this scanner's input can be interpreted as a byte value in the default radix using the `nextByte()` method.
`boolean`	`hasNextByte(int radix)`	Returns true if the next token in this scanner's input can be interpreted as a byte value in the specified radix using the `nextByte()` method.
`boolean`	`hasNextDouble()`	Returns true if the next token in this scanner's input can be interpreted as a double value using the `nextDouble()` method.
`boolean`	`hasNextFloat()`	Returns true if the next token in this scanner's input can be interpreted as a float value using the `nextFloat()` method.
`boolean`	`hasNextInt()`	Returns true if the next token in this scanner's input can be interpreted as an int value in the default radix using the `nextInt()` method.
`boolean`	`hasNextInt(int radix)`	Returns true if the next token in this scanner's input can be interpreted as an int value in the specified radix using the `nextInt()` method.
`boolean`	`hasNextLine()`	Returns true if there is another line in the input of this scanner.
`boolean`	`hasNextLong()`	Returns true if the next token in this scanner's input can be interpreted as a long value in the default radix using the `nextLong()` method.
`boolean`	`hasNextLong(int radix)`	Returns true if the next token in this scanner's input can be interpreted as a long value in the specified radix using the `nextLong()` method.
`boolean`	`hasNextShort()`	Returns true if the next token in this scanner's input can be interpreted as a short value in the default radix using the `nextShort()` method.
`boolean`	`hasNextShort(int radix)`	Returns true if the next token in this scanner's input can be interpreted as a short value in the specified radix using the `nextShort()` method.
`IOException`	`ioException()`	Returns the `IOException` last thrown by this `Scanner`'s underlying `Readable`.
`Locale`	`locale()`	Returns this scanner's locale.
`MatchResult`	`match()`	Returns the match result of the last scanning operation performed by this scanner.
`String`	`next()`	Finds and returns the next complete token from this scanner.
`String`	`next(String pattern)`	Returns the next token if it matches the pattern constructed from the specified string.
`String`	`next(Pattern pattern)`	Returns the next token if it matches the specified pattern.
`BigDecimal`	`nextBigDecimal()`	Scans the next token of the input as a `BigDecimal`.
`BigInteger`	`nextBigInteger()`	Scans the next token of the input as a `BigInteger`.
`BigInteger`	`nextBigInteger(int radix)`	Scans the next token of the input as a `BigInteger`.
`boolean`	`nextBoolean()`	Scans the next token of the input into a boolean value and returns that value.
`byte`	`nextByte()`	Scans the next token of the input as a `byte`.
`byte`	`nextByte(int radix)`	Scans the next token of the input as a `byte`.
`double`	`nextDouble()`	Scans the next token of the input as a `double`.
`float`	`nextFloat()`	Scans the next token of the input as a `float`.
`int`	`nextInt()`	Scans the next token of the input as an `int`.
`int`	`nextInt(int radix)`	Scans the next token of the input as an `int`.
`String`	`nextLine()`	Advances this scanner past the current line and returns the input that was skipped.
`long`	`nextLong()`	Scans the next token of the input as a `long`.
`long`	`nextLong(int radix)`	Scans the next token of the input as a `long`.
`short`	`nextShort()`	Scans the next token of the input as a `short`.
`short`	`nextShort(int radix)`	Scans the next token of the input as a `short`.
`int`	`radix()`	Returns this scanner's default radix.
`void`	`remove()`	The remove operation is not supported by this implementation of `Iterator`.
`Scanner`	`reset()`	Resets this scanner.
`Scanner`	`skip(String pattern)`	Skips input that matches a pattern constructed from the specified string.
`Scanner`	`skip(Pattern pattern)`	Skips input that matches the specified pattern, ignoring delimiters.
`Stream<String>`	`tokens()`	Returns a stream of delimiter-separated tokens from this scanner.
`String`	`toString()`	Returns the string representation of this `Scanner`.
`Scanner`	`useDelimiter(String pattern)`	Sets this scanner's delimiting pattern to a pattern constructed from the specified `String`.
`Scanner`	`useDelimiter(Pattern pattern)`	Sets this scanner's delimiting pattern to the specified pattern.
`Scanner`	`useLocale(Locale locale)`	Sets this scanner's locale to the specified locale.
`Scanner`	`useRadix(int radix)`	Sets this scanner's default radix to the specified radix.

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods declared in interface java.util.Iterator

forEachRemaining

Constructors

Scanner

public Scanner(Readable source)

Constructs a new Scanner that produces values scanned from the specified source.

Parameters:: source - A character source implementing the Readable interface

Scanner

public Scanner(InputStream source)

Constructs a new Scanner that produces values scanned from the specified input stream. Bytes from the stream are converted into characters using the underlying platform's default charset.

Parameters:: source - An input stream to be scanned

Scanner

public Scanner(InputStream source,
               String charsetName)

Constructs a new Scanner that produces values scanned from the specified input stream. Bytes from the stream are converted into characters using the specified charset.

Parameters:: source - An input stream to be scanned; charsetName - The encoding type used to convert bytes from the stream into characters to be scanned
Throws:: IllegalArgumentException - if the specified character set does not exist

Scanner

public Scanner(InputStream source,
               Charset charset)

Constructs a new Scanner that produces values scanned from the specified input stream. Bytes from the stream are converted into characters using the specified charset.

Parameters:: source - an input stream to be scanned; charset - the charset used to convert bytes from the file into characters to be scanned
Since:: 10

Scanner

public Scanner(File source)
        throws FileNotFoundException

Constructs a new Scanner that produces values scanned from the specified file. Bytes from the file are converted into characters using the underlying platform's default charset.

Parameters:: source - A file to be scanned
Throws:: FileNotFoundException - if source is not found

Scanner

public Scanner(File source,
               String charsetName)
        throws FileNotFoundException

Constructs a new Scanner that produces values scanned from the specified file. Bytes from the file are converted into characters using the specified charset.

Parameters:: source - A file to be scanned; charsetName - The encoding type used to convert bytes from the file into characters to be scanned
Throws:: FileNotFoundException - if source is not found; IllegalArgumentException - if the specified encoding is not found

Scanner

public Scanner(File source,
               Charset charset)
        throws IOException

Constructs a new Scanner that produces values scanned from the specified file. Bytes from the file are converted into characters using the specified charset.

Parameters:: source - A file to be scanned; charset - The charset used to convert bytes from the file into characters to be scanned
Throws:: IOException - if an I/O error occurs opening the source
Since:: 10

Scanner

public Scanner(Path source)
        throws IOException

Constructs a new Scanner that produces values scanned from the specified file. Bytes from the file are converted into characters using the underlying platform's default charset.

Parameters:: source - the path to the file to be scanned
Throws:: IOException - if an I/O error occurs opening source
Since:: 1.7

Scanner

public Scanner(Path source,
               String charsetName)
        throws IOException

Constructs a new Scanner that produces values scanned from the specified file. Bytes from the file are converted into characters using the specified charset.

Parameters:: source - the path to the file to be scanned; charsetName - The encoding type used to convert bytes from the file into characters to be scanned
Throws:: IOException - if an I/O error occurs opening source; IllegalArgumentException - if the specified encoding is not found
Since:: 1.7

Scanner

public Scanner(Path source,
               Charset charset)
        throws IOException

Constructs a new Scanner that produces values scanned from the specified file. Bytes from the file are converted into characters using the specified charset.

Parameters:: source - the path to the file to be scanned; charset - the charset used to convert bytes from the file into characters to be scanned
Throws:: IOException - if an I/O error occurs opening the source
Since:: 10

Scanner

public Scanner(String source)

Constructs a new Scanner that produces values scanned from the specified string.

Parameters:: source - A string to scan

Scanner

public Scanner(ReadableByteChannel source)

Constructs a new Scanner that produces values scanned from the specified channel. Bytes from the source are converted into characters using the underlying platform's default charset.

Parameters:: source - A channel to scan

Scanner

public Scanner(ReadableByteChannel source,
               String charsetName)

Constructs a new Scanner that produces values scanned from the specified channel. Bytes from the source are converted into characters using the specified charset.

Parameters:: source - A channel to scan; charsetName - The encoding type used to convert bytes from the channel into characters to be scanned
Throws:: IllegalArgumentException - if the specified character set does not exist

Scanner

public Scanner(ReadableByteChannel source,
               Charset charset)

Constructs a new Scanner that produces values scanned from the specified channel. Bytes from the source are converted into characters using the specified charset.

Parameters:: source - a channel to scan; charset - the encoding type used to convert bytes from the channel into characters to be scanned
Since:: 10

Methods

close

public void close()

Closes this scanner.

If this scanner has not yet been closed then if its underlying readable also implements the Closeable interface then the readable's close method will be invoked. If this scanner is already closed then invoking this method will have no effect.

Attempting to perform search operations after a scanner has been closed will result in an IllegalStateException.

Specified by:: close in interface AutoCloseable
Specified by:: close in interface Closeable

ioException

public IOException ioException()

Returns the IOException last thrown by this Scanner's underlying Readable. This method returns null if no such exception exists.

Returns:: the last exception thrown by this scanner's readable

delimiter

public Pattern delimiter()

Returns the Pattern this Scanner is currently using to match delimiters.

Returns:: this scanner's delimiting pattern.

useDelimiter

public Scanner useDelimiter(Pattern pattern)

Sets this scanner's delimiting pattern to the specified pattern.

Parameters:: pattern - A delimiting pattern
Returns:: this scanner

useDelimiter

public Scanner useDelimiter(String pattern)

Sets this scanner's delimiting pattern to a pattern constructed from the specified String.

An invocation of this method of the form useDelimiter(pattern) behaves in exactly the same way as the invocation useDelimiter(Pattern.compile(pattern)).

Invoking the reset() method will set the scanner's delimiter to the default.

Parameters:: pattern - A string specifying a delimiting pattern
Returns:: this scanner

locale

public Locale locale()

Returns this scanner's locale.

A scanner's locale affects many elements of its default primitive matching regular expressions; see localized numbers above.

Returns:: this scanner's locale

useLocale

public Scanner useLocale(Locale locale)

Sets this scanner's locale to the specified locale.

A scanner's locale affects many elements of its default primitive matching regular expressions; see localized numbers above.

Invoking the reset() method will set the scanner's locale to the initial locale.

Parameters:: locale - A string specifying the locale to use
Returns:: this scanner

radix

public int radix()

Returns this scanner's default radix.

A scanner's radix affects elements of its default number matching regular expressions; see localized numbers above.

Returns:: the default radix of this scanner

useRadix

public Scanner useRadix(int radix)

Sets this scanner's default radix to the specified radix.

A scanner's radix affects elements of its default number matching regular expressions; see localized numbers above.

If the radix is less than Character.MIN_RADIX or greater than Character.MAX_RADIX, then an IllegalArgumentException is thrown.

Invoking the reset() method will set the scanner's radix to 10.

Parameters:: radix - The radix to use when scanning numbers
Returns:: this scanner
Throws:: IllegalArgumentException - if radix is out of range

match

public MatchResult match()

Returns the match result of the last scanning operation performed by this scanner. This method throws IllegalStateException if no match has been performed, or if the last match was not successful.

The various next methods of Scanner make a match result available if they complete without throwing an exception. For instance, after an invocation of the nextInt() method that returned an int, this method returns a MatchResult for the search of the Integer regular expression defined above. Similarly the findInLine(), findWithinHorizon(), and skip() methods will make a match available if they succeed.

Returns:: a match result for the last match operation
Throws:: IllegalStateException - If no match result is available

toString

public String toString()

Returns the string representation of this Scanner. The string representation of a Scanner contains information that may be useful for debugging. The exact format is unspecified.

Overrides:: toString in class Object
Returns:: The string representation of this scanner

hasNext

public boolean hasNext()

Returns true if this scanner has another token in its input. This method may block while waiting for input to scan. The scanner does not advance past any input.

Specified by:: hasNext in interface Iterator<String>
Returns:: true if and only if this scanner has another token
Throws:: IllegalStateException - if this scanner is closed
See Also:: Iterator

remove

public void remove()

The remove operation is not supported by this implementation of Iterator.

Specified by:: remove in interface Iterator<String>
Throws:: UnsupportedOperationException - if this method is invoked.
See Also:: Iterator

hasNext

public boolean hasNext(String pattern)

Returns true if the next token matches the pattern constructed from the specified string. The scanner does not advance past any input.

An invocation of this method of the form hasNext(pattern) behaves in exactly the same way as the invocation hasNext(Pattern.compile(pattern)).

Parameters:: pattern - a string specifying the pattern to scan
Returns:: true if and only if this scanner has another token matching the specified pattern
Throws:: IllegalStateException - if this scanner is closed

hasNext

public boolean hasNext(Pattern pattern)

Returns true if the next complete token matches the specified pattern. A complete token is prefixed and postfixed by input that matches the delimiter pattern. This method may block while waiting for input. The scanner does not advance past any input.

Parameters:: pattern - the pattern to scan for
Returns:: true if and only if this scanner has another token matching the specified pattern
Throws:: IllegalStateException - if this scanner is closed

hasNextLine

public boolean hasNextLine()

Returns true if there is another line in the input of this scanner. This method may block while waiting for input. The scanner does not advance past any input.

Returns:: true if and only if this scanner has another line of input
Throws:: IllegalStateException - if this scanner is closed

nextLine

public String nextLine()

Advances this scanner past the current line and returns the input that was skipped. This method returns the rest of the current line, excluding any line separator at the end. The position is set to the beginning of the next line.

Since this method continues to search through the input looking for a line separator, it may buffer all of the input searching for the line to skip if no line separators are present.

Returns:: the line that was skipped
Throws:: NoSuchElementException - if no line was found; IllegalStateException - if this scanner is closed

findInLine

public String findInLine(String pattern)

Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.

An invocation of this method of the form findInLine(pattern) behaves in exactly the same way as the invocation findInLine(Pattern.compile(pattern)).

Parameters:: pattern - a string specifying the pattern to search for
Returns:: the text that matched the specified pattern
Throws:: IllegalStateException - if this scanner is closed

findInLine

public String findInLine(Pattern pattern)

Attempts to find the next occurrence of the specified pattern ignoring delimiters. If the pattern is found before the next line separator, the scanner advances past the input that matched and returns the string that matched the pattern. If no such pattern is detected in the input up to the next line separator, then null is returned and the scanner's position is unchanged. This method may block waiting for input that matches the pattern.

Since this method continues to search through the input looking for the specified pattern, it may buffer all of the input searching for the desired token if no line separators are present.

Parameters:: pattern - the pattern to scan for
Returns:: the text that matched the specified pattern
Throws:: IllegalStateException - if this scanner is closed

findWithinHorizon

public String findWithinHorizon(String pattern,
                                int horizon)

Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.

An invocation of this method of the form findWithinHorizon(pattern) behaves in exactly the same way as the invocation findWithinHorizon(Pattern.compile(pattern), horizon).

Parameters:: pattern - a string specifying the pattern to search for; horizon - the search horizon
Returns:: the text that matched the specified pattern
Throws:: IllegalStateException - if this scanner is closed; IllegalArgumentException - if horizon is negative

findWithinHorizon

public String findWithinHorizon(Pattern pattern,
                                int horizon)

Attempts to find the next occurrence of the specified pattern.

This method searches through the input up to the specified search horizon, ignoring delimiters. If the pattern is found the scanner advances past the input that matched and returns the string that matched the pattern. If no such pattern is detected then the null is returned and the scanner's position remains unchanged. This method may block waiting for input that matches the pattern.

A scanner will never search more than horizon code points beyond its current position. Note that a match may be clipped by the horizon; that is, an arbitrary match result may have been different if the horizon had been larger. The scanner treats the horizon as a transparent, non-anchoring bound (see Matcher.useTransparentBounds(boolean) and Matcher.useAnchoringBounds(boolean)).

If horizon is 0, then the horizon is ignored and this method continues to search through the input looking for the specified pattern without bound. In this case it may buffer all of the input searching for the pattern.

If horizon is negative, then an IllegalArgumentException is thrown.

Parameters:: pattern - the pattern to scan for; horizon - the search horizon
Returns:: the text that matched the specified pattern
Throws:: IllegalStateException - if this scanner is closed; IllegalArgumentException - if horizon is negative

skip

public Scanner skip(Pattern pattern)

Skips input that matches the specified pattern, ignoring delimiters. This method will skip input if an anchored match of the specified pattern succeeds.

If a match to the specified pattern is not found at the current position, then no input is skipped and a NoSuchElementException is thrown.

Since this method seeks to match the specified pattern starting at the scanner's current position, patterns that can match a lot of input (".*", for example) may cause the scanner to buffer a large amount of input.

Note that it is possible to skip something without risking a NoSuchElementException by using a pattern that can match nothing, e.g., sc.skip("[ \t]*").

Parameters:: pattern - a string specifying the pattern to skip over
Returns:: this scanner
Throws:: NoSuchElementException - if the specified pattern is not found; IllegalStateException - if this scanner is closed

skip

public Scanner skip(String pattern)

Skips input that matches a pattern constructed from the specified string.

An invocation of this method of the form skip(pattern) behaves in exactly the same way as the invocation skip(Pattern.compile(pattern)).

Parameters:: pattern - a string specifying the pattern to skip over
Returns:: this scanner
Throws:: IllegalStateException - if this scanner is closed

hasNextBoolean

public boolean hasNextBoolean()

Returns true if the next token in this scanner's input can be interpreted as a boolean value using a case insensitive pattern created from the string "true|false". The scanner does not advance past the input that matched.

Returns:: true if and only if this scanner's next token is a valid boolean value
Throws:: IllegalStateException - if this scanner is closed

nextBoolean

public boolean nextBoolean()

Scans the next token of the input into a boolean value and returns that value. This method will throw InputMismatchException if the next token cannot be translated into a valid boolean value. If the match is successful, the scanner advances past the input that matched.

Returns:: the boolean scanned from the input
Throws:: InputMismatchException - if the next token is not a valid boolean; NoSuchElementException - if input is exhausted; IllegalStateException - if this scanner is closed

hasNextByte

public boolean hasNextByte()

Returns true if the next token in this scanner's input can be interpreted as a byte value in the default radix using the nextByte() method. The scanner does not advance past any input.

Returns:: true if and only if this scanner's next token is a valid byte value
Throws:: IllegalStateException - if this scanner is closed

hasNextByte

public boolean hasNextByte(int radix)

Returns true if the next token in this scanner's input can be interpreted as a byte value in the specified radix using the nextByte() method. The scanner does not advance past any input.

If the radix is less than Character.MIN_RADIX or greater than Character.MAX_RADIX, then an IllegalArgumentException is thrown.

Parameters:: radix - the radix used to interpret the token as a byte value
Returns:: true if and only if this scanner's next token is a valid byte value
Throws:: IllegalStateException - if this scanner is closed; IllegalArgumentException - if the radix is out of range

nextByte

public byte nextByte()

Scans the next token of the input as a byte.

An invocation of this method of the form nextByte() behaves in exactly the same way as the invocation nextByte(radix), where radix is the default radix of this scanner.

Returns:: the byte scanned from the input
Throws:: InputMismatchException - if the next token does not match the Integer regular expression, or is out of range; NoSuchElementException - if input is exhausted; IllegalStateException - if this scanner is closed

nextByte

public byte nextByte(int radix)

Scans the next token of the input as a byte. This method will throw InputMismatchException if the next token cannot be translated into a valid byte value as described below. If the translation is successful, the scanner advances past the input that matched.

If the next token matches the Integer regular expression defined above then the token is converted into a byte value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits via Character.digit, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Byte.parseByte with the specified radix.

If the radix is less than Character.MIN_RADIX or greater than Character.MAX_RADIX, then an IllegalArgumentException is thrown.

Parameters:: radix - the radix used to interpret the token as a byte value
Returns:: the byte scanned from the input
Throws:: InputMismatchException - if the next token does not match the Integer regular expression, or is out of range; NoSuchElementException - if input is exhausted; IllegalStateException - if this scanner is closed; IllegalArgumentException - if the radix is out of range

hasNextShort

public boolean hasNextShort()

Returns true if the next token in this scanner's input can be interpreted as a short value in the default radix using the nextShort() method. The scanner does not advance past any input.

Returns:: true if and only if this scanner's next token is a valid short value in the default radix
Throws:: IllegalStateException - if this scanner is closed

hasNextShort

public boolean hasNextShort(int radix)

Returns true if the next token in this scanner's input can be interpreted as a short value in the specified radix using the nextShort() method. The scanner does not advance past any input.

If the radix is less than Character.MIN_RADIX or greater than Character.MAX_RADIX, then an IllegalArgumentException is thrown.

Parameters:: radix - the radix used to interpret the token as a short value
Returns:: true if and only if this scanner's next token is a valid short value in the specified radix
Throws:: IllegalStateException - if this scanner is closed; IllegalArgumentException - if the radix is out of range

nextShort

public short nextShort()

Scans the next token of the input as a short.

An invocation of this method of the form nextShort() behaves in exactly the same way as the invocation nextShort(radix), where radix is the default radix of this scanner.

Returns:: the short scanned from the input
Throws:: InputMismatchException - if the next token does not match the Integer regular expression, or is out of range; NoSuchElementException - if input is exhausted; IllegalStateException - if this scanner is closed

nextShort

public short nextShort(int radix)

Scans the next token of the input as a short. This method will throw InputMismatchException if the next token cannot be translated into a valid short value as described below. If the translation is successful, the scanner advances past the input that matched.

If the next token matches the Integer regular expression defined above then the token is converted into a short value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits via Character.digit, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Short.parseShort with the specified radix.

If the radix is less than Character.MIN_RADIX or greater than Character.MAX_RADIX, then an IllegalArgumentException is thrown.

Parameters:: radix - the radix used to interpret the token as a short value
Returns:: the short scanned from the input
Throws:: InputMismatchException - if the next token does not match the Integer regular expression, or is out of range; NoSuchElementException - if input is exhausted; IllegalStateException - if this scanner is closed; IllegalArgumentException - if the radix is out of range

hasNextInt

public boolean hasNextInt()

Returns true if the next token in this scanner's input can be interpreted as an int value in the default radix using the nextInt() method. The scanner does not advance past any input.

Returns:: true if and only if this scanner's next token is a valid int value
Throws:: IllegalStateException - if this scanner is closed

hasNextInt

public boolean hasNextInt(int radix)

Returns true if the next token in this scanner's input can be interpreted as an int value in the specified radix using the nextInt() method. The scanner does not advance past any input.

If the radix is less than Character.MIN_RADIX or greater than Character.MAX_RADIX, then an IllegalArgumentException is thrown.

Parameters:: radix - the radix used to interpret the token as an int value
Returns:: true if and only if this scanner's next token is a valid int value
Throws:: IllegalStateException - if this scanner is closed; IllegalArgumentException - if the radix is out of range

nextInt

public int nextInt()

Scans the next token of the input as an int.

An invocation of this method of the form nextInt() behaves in exactly the same way as the invocation nextInt(radix), where radix is the default radix of this scanner.

Returns:: the int scanned from the input
Throws:: InputMismatchException - if the next token does not match the Integer regular expression, or is out of range; NoSuchElementException - if input is exhausted; IllegalStateException - if this scanner is closed

nextInt

public int nextInt(int radix)

Scans the next token of the input as an int. This method will throw InputMismatchException if the next token cannot be translated into a valid int value as described below. If the translation is successful, the scanner advances past the input that matched.

If the next token matches the Integer regular expression defined above then the token is converted into an int value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits via Character.digit, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Integer.parseInt with the specified radix.

If the radix is less than Character.MIN_RADIX or greater than Character.MAX_RADIX, then an IllegalArgumentException is thrown.

Parameters:: radix - the radix used to interpret the token as an int value
Returns:: the int scanned from the input
Throws:: InputMismatchException - if the next token does not match the Integer regular expression, or is out of range; NoSuchElementException - if input is exhausted; IllegalStateException - if this scanner is closed; IllegalArgumentException - if the radix is out of range

hasNextLong

public boolean hasNextLong()

Returns true if the next token in this scanner's input can be interpreted as a long value in the default radix using the nextLong() method. The scanner does not advance past any input.

Returns:: true if and only if this scanner's next token is a valid long value
Throws:: IllegalStateException - if this scanner is closed

hasNextLong

public boolean hasNextLong(int radix)

Returns true if the next token in this scanner's input can be interpreted as a long value in the specified radix using the nextLong() method. The scanner does not advance past any input.

If the radix is less than Character.MIN_RADIX or greater than Character.MAX_RADIX, then an IllegalArgumentException is thrown.

Parameters:: radix - the radix used to interpret the token as a long value
Returns:: true if and only if this scanner's next token is a valid long value
Throws:: IllegalStateException - if this scanner is closed; IllegalArgumentException - if the radix is out of range

nextLong

public long nextLong()

Scans the next token of the input as a long.

An invocation of this method of the form nextLong() behaves in exactly the same way as the invocation nextLong(radix), where radix is the default radix of this scanner.

Returns:: the long scanned from the input
Throws:: InputMismatchException - if the next token does not match the Integer regular expression, or is out of range; NoSuchElementException - if input is exhausted; IllegalStateException - if this scanner is closed

nextLong

public long nextLong(int radix)

Scans the next token of the input as a long. This method will throw InputMismatchException if the next token cannot be translated into a valid long value as described below. If the translation is successful, the scanner advances past the input that matched.

If the next token matches the Integer regular expression defined above then the token is converted into a long value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits via Character.digit, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Long.parseLong with the specified radix.

If the radix is less than Character.MIN_RADIX or greater than Character.MAX_RADIX, then an IllegalArgumentException is thrown.

Parameters:: radix - the radix used to interpret the token as an int value
Returns:: the long scanned from the input
Throws:: InputMismatchException - if the next token does not match the Integer regular expression, or is out of range; NoSuchElementException - if input is exhausted; IllegalStateException - if this scanner is closed; IllegalArgumentException - if the radix is out of range

hasNextFloat

public boolean hasNextFloat()

Returns true if the next token in this scanner's input can be interpreted as a float value using the nextFloat() method. The scanner does not advance past any input.

Returns:: true if and only if this scanner's next token is a valid float value
Throws:: IllegalStateException - if this scanner is closed

nextFloat

public float nextFloat()

Scans the next token of the input as a float. This method will throw InputMismatchException if the next token cannot be translated into a valid float value as described below. If the translation is successful, the scanner advances past the input that matched.

If the next token matches the Float regular expression defined above then the token is converted into a float value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits via Character.digit, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Float.parseFloat. If the token matches the localized NaN or infinity strings, then either "Nan" or "Infinity" is passed to Float.parseFloat as appropriate.

Returns:: the float scanned from the input
Throws:: InputMismatchException - if the next token does not match the Float regular expression, or is out of range; NoSuchElementException - if input is exhausted; IllegalStateException - if this scanner is closed

hasNextDouble

public boolean hasNextDouble()

Returns true if the next token in this scanner's input can be interpreted as a double value using the nextDouble() method. The scanner does not advance past any input.

Returns:: true if and only if this scanner's next token is a valid double value
Throws:: IllegalStateException - if this scanner is closed

nextDouble

public double nextDouble()

Scans the next token of the input as a double. This method will throw InputMismatchException if the next token cannot be translated into a valid double value. If the translation is successful, the scanner advances past the input that matched.

If the next token matches the Float regular expression defined above then the token is converted into a double value as if by removing all locale specific prefixes, group separators, and locale specific suffixes, then mapping non-ASCII digits into ASCII digits via Character.digit, prepending a negative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Double.parseDouble. If the token matches the localized NaN or infinity strings, then either "Nan" or "Infinity" is passed to Double.parseDouble as appropriate.

Returns:: the double scanned from the input
Throws:: InputMismatchException - if the next token does not match the Float regular expression, or is out of range; NoSuchElementException - if the input is exhausted; IllegalStateException - if this scanner is closed

hasNextBigInteger

public boolean hasNextBigInteger()

Returns true if the next token in this scanner's input can be interpreted as a BigInteger in the default radix using the nextBigInteger() method. The scanner does not advance past any input.

Returns:: true if and only if this scanner's next token is a valid BigInteger
Throws:: IllegalStateException - if this scanner is closed

hasNextBigInteger

public boolean hasNextBigInteger(int radix)

Returns true if the next token in this scanner's input can be interpreted as a BigInteger in the specified radix using the nextBigInteger() method. The scanner does not advance past any input.

If the radix is less than Character.MIN_RADIX or greater than Character.MAX_RADIX, then an IllegalArgumentException is thrown.

Parameters:: radix - the radix used to interpret the token as an integer
Returns:: true if and only if this scanner's next token is a valid BigInteger
Throws:: IllegalStateException - if this scanner is closed; IllegalArgumentException - if the radix is out of range

nextBigInteger

public BigInteger nextBigInteger()

Scans the next token of the input as a BigInteger.

An invocation of this method of the form nextBigInteger() behaves in exactly the same way as the invocation nextBigInteger(radix), where radix is the default radix of this scanner.

Returns:: the BigInteger scanned from the input
Throws:: InputMismatchException - if the next token does not match the Integer regular expression, or is out of range; NoSuchElementException - if the input is exhausted; IllegalStateException - if this scanner is closed

nextBigInteger

public BigInteger nextBigInteger(int radix)

Scans the next token of the input as a BigInteger.

If the next token matches the Integer regular expression defined above then the token is converted into a BigInteger value as if by removing all group separators, mapping non-ASCII digits into ASCII digits via the Character.digit, and passing the resulting string to the BigInteger(String, int) constructor with the specified radix.

If the radix is less than Character.MIN_RADIX or greater than Character.MAX_RADIX, then an IllegalArgumentException is thrown.

Parameters:: radix - the radix used to interpret the token
Returns:: the BigInteger scanned from the input
Throws:: InputMismatchException - if the next token does not match the Integer regular expression, or is out of range; NoSuchElementException - if the input is exhausted; IllegalStateException - if this scanner is closed; IllegalArgumentException - if the radix is out of range

hasNextBigDecimal

public boolean hasNextBigDecimal()

Returns true if the next token in this scanner's input can be interpreted as a BigDecimal using the nextBigDecimal() method. The scanner does not advance past any input.

Returns:: true if and only if this scanner's next token is a valid BigDecimal
Throws:: IllegalStateException - if this scanner is closed

nextBigDecimal

public BigDecimal nextBigDecimal()

Scans the next token of the input as a BigDecimal.

If the next token matches the Decimal regular expression defined above then the token is converted into a BigDecimal value as if by removing all group separators, mapping non-ASCII digits into ASCII digits via the Character.digit, and passing the resulting string to the BigDecimal(String) constructor.

Returns:: the BigDecimal scanned from the input
Throws:: InputMismatchException - if the next token does not match the Decimal regular expression, or is out of range; NoSuchElementException - if the input is exhausted; IllegalStateException - if this scanner is closed

reset

public Scanner reset()

Resets this scanner.

Resetting a scanner discards all of its explicit state information which may have been changed by invocations of useDelimiter(), useLocale(), or useRadix().

An invocation of this method of the form scanner.reset() behaves in exactly the same way as the invocation

scanner.useDelimiter("\\p{javaWhitespace}+")
       .useLocale(Locale.getDefault(Locale.Category.FORMAT))
       .useRadix(10);

Returns:: this scanner
Since:: 1.6

tokens

public Stream<String> tokens()

Returns a stream of delimiter-separated tokens from this scanner. The stream contains the same tokens that would be returned, starting from this scanner's current state, by calling the next() method repeatedly until the hasNext() method returns false.

The resulting stream is sequential and ordered. All stream elements are non-null.

Scanning starts upon initiation of the terminal stream operation, using the current state of this scanner. Subsequent calls to any methods on this scanner other than close() and ioException() may return undefined results or may cause undefined effects on the returned stream. The returned stream's source Spliterator is fail-fast and will, on a best-effort basis, throw a ConcurrentModificationException if any such calls are detected during stream pipeline execution.

After stream pipeline execution completes, this scanner is left in an indeterminate state and cannot be reused.

If this scanner contains a resource that must be released, this scanner should be closed, either by calling its close() method, or by closing the returned stream. Closing the stream will close the underlying scanner. IllegalStateException is thrown if the scanner has been closed when this method is called, or if this scanner is closed during stream pipeline execution.

This method might block waiting for more input.

API Note:

For example, the following code will create a list of comma-delimited tokens from a string:

List<String> result = new Scanner("abc,def,,ghi")
     .useDelimiter(",")
     .tokens()
     .collect(Collectors.toList());

The resulting list would contain "abc", "def", the empty string, and "ghi".

Returns:

a sequential stream of token strings

Throws:

IllegalStateException - if this scanner is closed

Since:

9

findAll

public Stream<MatchResult> findAll(Pattern pattern)

Returns a stream of match results from this scanner. The stream contains the same results in the same order that would be returned by calling findWithinHorizon(pattern, 0) and then match() successively as long as findWithinHorizon() finds matches.

The resulting stream is sequential and ordered. All stream elements are non-null.

Scanning starts upon initiation of the terminal stream operation, using the current state of this scanner. Subsequent calls to any methods on this scanner other than close() and ioException() may return undefined results or may cause undefined effects on the returned stream. The returned stream's source Spliterator is fail-fast and will, on a best-effort basis, throw a ConcurrentModificationException if any such calls are detected during stream pipeline execution.

After stream pipeline execution completes, this scanner is left in an indeterminate state and cannot be reused.

If this scanner contains a resource that must be released, this scanner should be closed, either by calling its close() method, or by closing the returned stream. Closing the stream will close the underlying scanner. IllegalStateException is thrown if the scanner has been closed when this method is called, or if this scanner is closed during stream pipeline execution.

As with the findWithinHorizon() methods, this method might block waiting for additional input, and it might buffer an unbounded amount of input searching for a match.

API Note:

For example, the following code will read a file and return a list of all sequences of characters consisting of seven or more Latin capital letters:

try (Scanner sc = new Scanner(Path.of("input.txt"))) {
     Pattern pat = Pattern.compile("[A-Z]{7,}");
     List<String> capWords = sc.findAll(pat)
                               .map(MatchResult::group)
                               .collect(Collectors.toList());
 }

Parameters:

pattern - the pattern to be matched

Returns:

a sequential stream of match results

Throws:

NullPointerException - if pattern is null

IllegalStateException - if this scanner is closed

Since:

9

findAll

public Stream<MatchResult> findAll(String patString)

Returns a stream of match results that match the provided pattern string. The effect is equivalent to the following code:

scanner.findAll(Pattern.compile(patString))

Parameters:: patString - the pattern string
Returns:: a sequential stream of match results
Throws:: NullPointerException - if patString is null; IllegalStateException - if this scanner is closed; PatternSyntaxException - if the regular expression's syntax is invalid
Since:: 9
See Also:: Pattern

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Scanner.html