Class BigInteger

Fields

ZERO

public static final BigInteger ZERO

The BigInteger constant zero.

Since:

1.2

ONE

public static final BigInteger ONE

The BigInteger constant one.

Since:

1.2

TWO

public static final BigInteger TWO

The BigInteger constant two.

Since:

9

TEN

public static final BigInteger TEN

The BigInteger constant ten.

Since:

1.5

Constructors

BigInteger

public BigInteger(byte[] val,
                  int off,
                  int len)

Translates a byte sub-array containing the two's-complement binary representation of a BigInteger into a BigInteger. The sub-array is specified via an offset into the array and a length. The sub-array is assumed to be in big-endian byte-order: the most significant byte is the element at index off. The val array is assumed to be unchanged for the duration of the constructor call. An IndexOutOfBoundsException is thrown if the length of the array val is non-zero and either off is negative, len is negative, or off+len is greater than the length of val.

Parameters:

val - byte array containing a sub-array which is the big-endian two's-complement binary representation of a BigInteger.

off - the start offset of the binary representation.

len - the number of bytes to use.

Throws:

NumberFormatException - val is zero bytes long.

IndexOutOfBoundsException - if the provided array offset and length would cause an index into the byte array to be negative or greater than or equal to the array length.

Since:

9

BigInteger

public BigInteger(byte[] val)

Translates a byte array containing the two's-complement binary representation of a BigInteger into a BigInteger. The input array is assumed to be in big-endian byte-order: the most significant byte is in the zeroth element. The val array is assumed to be unchanged for the duration of the constructor call.

Parameters:

val - big-endian two's-complement binary representation of a BigInteger.

Throws:

NumberFormatException - val is zero bytes long.

BigInteger

public BigInteger(int signum,
                  byte[] magnitude,
                  int off,
                  int len)

Translates the sign-magnitude representation of a BigInteger into a BigInteger. The sign is represented as an integer signum value: -1 for negative, 0 for zero, or 1 for positive. The magnitude is a sub-array of a byte array in big-endian byte-order: the most significant byte is the element at index off. A zero value of the length len is permissible, and will result in a BigInteger value of 0, whether signum is -1, 0 or 1. The magnitude array is assumed to be unchanged for the duration of the constructor call. An IndexOutOfBoundsException is thrown if the length of the array magnitude is non-zero and either off is negative, len is negative, or off+len is greater than the length of magnitude.

Parameters:

signum - signum of the number (-1 for negative, 0 for zero, 1 for positive).

magnitude - big-endian binary representation of the magnitude of the number.

off - the start offset of the binary representation.

len - the number of bytes to use.

Throws:

NumberFormatException - signum is not one of the three legal values (-1, 0, and 1), or signum is 0 and magnitude contains one or more non-zero bytes.

IndexOutOfBoundsException - if the provided array offset and length would cause an index into the byte array to be negative or greater than or equal to the array length.

Since:

9

BigInteger

public BigInteger(int signum,
                  byte[] magnitude)

Translates the sign-magnitude representation of a BigInteger into a BigInteger. The sign is represented as an integer signum value: -1 for negative, 0 for zero, or 1 for positive. The magnitude is a byte array in big-endian byte-order: the most significant byte is the zeroth element. A zero-length magnitude array is permissible, and will result in a BigInteger value of 0, whether signum is -1, 0 or 1. The magnitude array is assumed to be unchanged for the duration of the constructor call.

Parameters:

signum - signum of the number (-1 for negative, 0 for zero, 1 for positive).

magnitude - big-endian binary representation of the magnitude of the number.

Throws:

NumberFormatException - signum is not one of the three legal values (-1, 0, and 1), or signum is 0 and magnitude contains one or more non-zero bytes.

BigInteger

public BigInteger(String val,
                  int radix)

Translates the String representation of a BigInteger in the specified radix into a BigInteger. The String representation consists of an optional minus or plus sign followed by a sequence of one or more digits in the specified radix. The character-to-digit mapping is provided by Character.digit. The String may not contain any extraneous characters (whitespace, for example).

Parameters:

val - String representation of BigInteger.

radix - radix to be used in interpreting val.

Throws:

NumberFormatException - val is not a valid representation of a BigInteger in the specified radix, or radix is outside the range from Character.MIN_RADIX to Character.MAX_RADIX, inclusive.

See Also:

Character.digit(char, int)

BigInteger

public BigInteger(String val)

Translates the decimal String representation of a BigInteger into a BigInteger. The String representation consists of an optional minus sign followed by a sequence of one or more decimal digits. The character-to-digit mapping is provided by Character.digit. The String may not contain any extraneous characters (whitespace, for example).

Parameters:

val - decimal String representation of BigInteger.

Throws:

NumberFormatException - val is not a valid representation of a BigInteger.

See Also:

Character.digit(char, int)

BigInteger

public BigInteger(int numBits,
                  Random rnd)

Constructs a randomly generated BigInteger, uniformly distributed over the range 0 to (2^numBits - 1), inclusive. The uniformity of the distribution assumes that a fair source of random bits is provided in rnd. Note that this constructor always constructs a non-negative BigInteger.

Parameters:

numBits - maximum bitLength of the new BigInteger.

rnd - source of randomness to be used in computing the new BigInteger.

Throws:

IllegalArgumentException - numBits is negative.

See Also:

bitLength()

BigInteger

public BigInteger(int bitLength,
                  int certainty,
                  Random rnd)

Constructs a randomly generated positive BigInteger that is probably prime, with the specified bitLength.

API Note:

It is recommended that the probablePrime method be used in preference to this constructor unless there is a compelling need to specify a certainty.

Parameters:

bitLength - bitLength of the returned BigInteger.

certainty - a measure of the uncertainty that the caller is willing to tolerate. The probability that the new BigInteger represents a prime number will exceed (1 - 1/2^certainty). The execution time of this constructor is proportional to the value of this parameter.

rnd - source of random bits used to select candidates to be tested for primality.

Throws:

ArithmeticException - bitLength < 2 or bitLength is too large.

See Also:

bitLength()

Methods

probablePrime

public static BigInteger probablePrime(int bitLength,
                                       Random rnd)

Returns a positive BigInteger that is probably prime, with the specified bitLength. The probability that a BigInteger returned by this method is composite does not exceed 2^-100.

Parameters:

bitLength - bitLength of the returned BigInteger.

rnd - source of random bits used to select candidates to be tested for primality.

Returns:

a BigInteger of bitLength bits that is probably prime

Throws:

ArithmeticException - bitLength < 2 or bitLength is too large.

Since:

1.4

See Also:

bitLength()

nextProbablePrime

public BigInteger nextProbablePrime()

Returns the first integer greater than this BigInteger that is probably prime. The probability that the number returned by this method is composite does not exceed 2^-100. This method will never skip over a prime when searching: if it returns p, there is no prime q such that this < q < p.

Returns:

the first integer greater than this BigInteger that is probably prime.

Throws:

ArithmeticException - this < 0 or this is too large.

Since:

1.5

valueOf

public static BigInteger valueOf(long val)

Returns a BigInteger whose value is equal to that of the specified long.

API Note:

This static factory method is provided in preference to a (long) constructor because it allows for reuse of frequently used BigIntegers.

Parameters:

val - value of the BigInteger to return.

Returns:

a BigInteger with the specified value.

add

public BigInteger add(BigInteger val)

Returns a BigInteger whose value is (this + val).

Parameters:

val - value to be added to this BigInteger.

Returns:

this + val

subtract

public BigInteger subtract(BigInteger val)

Returns a BigInteger whose value is (this - val).

Parameters:

val - value to be subtracted from this BigInteger.

Returns:

this - val

multiply

public BigInteger multiply(BigInteger val)

Returns a BigInteger whose value is (this * val).

Implementation Note:

An implementation may offer better algorithmic performance when val == this.

Parameters:

val - value to be multiplied by this BigInteger.

Returns:

this * val

divide

public BigInteger divide(BigInteger val)

Returns a BigInteger whose value is (this / val).

Parameters:

val - value by which this BigInteger is to be divided.

Returns:

this / val

Throws:

ArithmeticException - if val is zero.

divideAndRemainder

public BigInteger[] divideAndRemainder(BigInteger val)

Returns an array of two BigIntegers containing (this / val) followed by (this % val).

Parameters:

val - value by which this BigInteger is to be divided, and the remainder computed.

Returns:

an array of two BigIntegers: the quotient (this / val) is the initial element, and the remainder (this % val) is the final element.

Throws:

ArithmeticException - if val is zero.

remainder

public BigInteger remainder(BigInteger val)

Returns a BigInteger whose value is (this % val).

Parameters:

val - value by which this BigInteger is to be divided, and the remainder computed.

Returns:

this % val

Throws:

ArithmeticException - if val is zero.

pow

public BigInteger pow(int exponent)

Returns a BigInteger whose value is (thisexponent). Note that exponent is an integer rather than a BigInteger.

Parameters:

exponent - exponent to which this BigInteger is to be raised.

Returns:

thisexponent

Throws:

ArithmeticException - exponent is negative. (This would cause the operation to yield a non-integer value.)

sqrt

public BigInteger sqrt()

Returns the integer square root of this BigInteger. The integer square root of the corresponding mathematical integer n is the largest mathematical integer s such that s*s <= n. It is equal to the value of floor(sqrt(n)), where sqrt(n) denotes the real square root of n treated as a real. Note that the integer square root will be less than the real square root if the latter is not representable as an integral value.

Returns:

the integer square root of this

Throws:

ArithmeticException - if this is negative. (The square root of a negative integer val is (i * sqrt(-val)) where i is the imaginary unit and is equal to sqrt(-1).)

Since:

9

sqrtAndRemainder

public BigInteger[] sqrtAndRemainder()

Returns an array of two BigIntegers containing the integer square root s of this and its remainder this - s*s, respectively.

Returns:

an array of two BigIntegers with the integer square root at offset 0 and the remainder at offset 1

Throws:

ArithmeticException - if this is negative. (The square root of a negative integer val is (i * sqrt(-val)) where i is the imaginary unit and is equal to sqrt(-1).)

Since:

9

See Also:

sqrt()

gcd

public BigInteger gcd(BigInteger val)

Returns a BigInteger whose value is the greatest common divisor of abs(this) and abs(val). Returns 0 if this == 0 && val == 0.

Parameters:

val - value with which the GCD is to be computed.

Returns:

GCD(abs(this), abs(val))

abs

public BigInteger abs()

Returns a BigInteger whose value is the absolute value of this BigInteger.

Returns:

abs(this)

negate

public BigInteger negate()

Returns a BigInteger whose value is (-this).

Returns:

-this

signum

public int signum()

Returns the signum function of this BigInteger.

Returns:

-1, 0 or 1 as the value of this BigInteger is negative, zero or positive.

mod

public BigInteger mod(BigInteger m)

Returns a BigInteger whose value is (this mod m). This method differs from remainder in that it always returns a non-negative BigInteger.

Parameters:

m - the modulus.

Returns:

this mod m

Throws:

ArithmeticException - m ≤ 0

See Also:

remainder(java.math.BigInteger)

modPow

public BigInteger modPow(BigInteger exponent,
                         BigInteger m)

Returns a BigInteger whose value is (thisexponent mod m). (Unlike pow, this method permits negative exponents.)

Parameters:

exponent - the exponent.

m - the modulus.

Returns:

thisexponent mod m

Throws:

ArithmeticException - m ≤ 0 or the exponent is negative and this BigInteger is not relatively prime to m.

See Also:

modInverse(java.math.BigInteger)

modInverse

public BigInteger modInverse(BigInteger m)

Returns a BigInteger whose value is (this^-1 mod m).

Parameters:

m - the modulus.

Returns:

this^-1 mod m.

Throws:

ArithmeticException - m ≤ 0, or this BigInteger has no multiplicative inverse mod m (that is, this BigInteger is not relatively prime to m).

shiftLeft

public BigInteger shiftLeft(int n)

Returns a BigInteger whose value is (this << n). The shift distance, n, may be negative, in which case this method performs a right shift. (Computes floor(this * 2n).)

Parameters:

n - shift distance, in bits.

Returns:

this << n

See Also:

shiftRight(int)

shiftRight

public BigInteger shiftRight(int n)

Returns a BigInteger whose value is (this >> n). Sign extension is performed. The shift distance, n, may be negative, in which case this method performs a left shift. (Computes floor(this / 2n).)

Parameters:

n - shift distance, in bits.

Returns:

this >> n

See Also:

shiftLeft(int)

and

public BigInteger and(BigInteger val)

Returns a BigInteger whose value is (this & val). (This method returns a negative BigInteger if and only if this and val are both negative.)

Parameters:

val - value to be AND'ed with this BigInteger.

Returns:

this & val

or

public BigInteger or(BigInteger val)

Returns a BigInteger whose value is (this | val). (This method returns a negative BigInteger if and only if either this or val is negative.)

Parameters:

val - value to be OR'ed with this BigInteger.

Returns:

this | val

xor

public BigInteger xor(BigInteger val)

Returns a BigInteger whose value is (this ^ val). (This method returns a negative BigInteger if and only if exactly one of this and val are negative.)

Parameters:

val - value to be XOR'ed with this BigInteger.

Returns:

this ^ val

not

public BigInteger not()

Returns a BigInteger whose value is (~this). (This method returns a negative value if and only if this BigInteger is non-negative.)

Returns:

~this

andNot

public BigInteger andNot(BigInteger val)

Returns a BigInteger whose value is (this & ~val). This method, which is equivalent to and(val.not()), is provided as a convenience for masking operations. (This method returns a negative BigInteger if and only if this is negative and val is positive.)

Parameters:

val - value to be complemented and AND'ed with this BigInteger.

Returns:

this & ~val

testBit

public boolean testBit(int n)

Returns true if and only if the designated bit is set. (Computes ((this & (1<<n)) != 0).)

Parameters:

n - index of bit to test.

Returns:

true if and only if the designated bit is set.

Throws:

ArithmeticException - n is negative.

setBit

public BigInteger setBit(int n)

Returns a BigInteger whose value is equivalent to this BigInteger with the designated bit set. (Computes (this | (1<<n)).)

Parameters:

n - index of bit to set.

Returns:

this | (1<<n)

Throws:

ArithmeticException - n is negative.

clearBit

public BigInteger clearBit(int n)

Returns a BigInteger whose value is equivalent to this BigInteger with the designated bit cleared. (Computes (this & ~(1<<n)).)

Parameters:

n - index of bit to clear.

Returns:

this & ~(1<<n)

Throws:

ArithmeticException - n is negative.

flipBit

public BigInteger flipBit(int n)

Returns a BigInteger whose value is equivalent to this BigInteger with the designated bit flipped. (Computes (this ^ (1<<n)).)

Parameters:

n - index of bit to flip.

Returns:

this ^ (1<<n)

Throws:

ArithmeticException - n is negative.

getLowestSetBit

public int getLowestSetBit()

Returns the index of the rightmost (lowest-order) one bit in this BigInteger (the number of zero bits to the right of the rightmost one bit). Returns -1 if this BigInteger contains no one bits. (Computes (this == 0? -1 : log2(this & -this)).)

Returns:

index of the rightmost one bit in this BigInteger.

bitLength

public int bitLength()

Returns the number of bits in the minimal two's-complement representation of this BigInteger, excluding a sign bit. For positive BigIntegers, this is equivalent to the number of bits in the ordinary binary representation. For zero this method returns 0. (Computes (ceil(log2(this < 0 ? -this : this+1))).)

Returns:

number of bits in the minimal two's-complement representation of this BigInteger, excluding a sign bit.

bitCount

public int bitCount()

Returns the number of bits in the two's complement representation of this BigInteger that differ from its sign bit. This method is useful when implementing bit-vector style sets atop BigIntegers.

Returns:

number of bits in the two's complement representation of this BigInteger that differ from its sign bit.

isProbablePrime

public boolean isProbablePrime(int certainty)

Returns true if this BigInteger is probably prime, false if it's definitely composite. If certainty is ≤ 0, true is returned.

Parameters:

certainty - a measure of the uncertainty that the caller is willing to tolerate: if the call returns true the probability that this BigInteger is prime exceeds (1 - 1/2^certainty). The execution time of this method is proportional to the value of this parameter.

Returns:

true if this BigInteger is probably prime, false if it's definitely composite.

compareTo

public int compareTo(BigInteger val)

Compares this BigInteger with the specified BigInteger. This method is provided in preference to individual methods for each of the six boolean comparison operators (<, ==, >, >=, !=, <=). The suggested idiom for performing these comparisons is: (x.compareTo(y) <op> 0), where <op> is one of the six comparison operators.

Specified by:

compareTo in interface Comparable<BigInteger>

Parameters:

val - BigInteger to which this BigInteger is to be compared.

Returns:

-1, 0 or 1 as this BigInteger is numerically less than, equal to, or greater than val.

equals

public boolean equals(Object x)

Compares this BigInteger with the specified Object for equality.

Overrides:

equals in class Object

Parameters:

x - Object to which this BigInteger is to be compared.

Returns:

true if and only if the specified Object is a BigInteger whose value is numerically equal to this BigInteger.

See Also:

Object.hashCode(), HashMap

min

public BigInteger min(BigInteger val)

Returns the minimum of this BigInteger and val.

Parameters:

val - value with which the minimum is to be computed.

Returns:

the BigInteger whose value is the lesser of this BigInteger and val. If they are equal, either may be returned.

max

public BigInteger max(BigInteger val)

Returns the maximum of this BigInteger and val.

Parameters:

val - value with which the maximum is to be computed.

Returns:

the BigInteger whose value is the greater of this and val. If they are equal, either may be returned.

hashCode

public int hashCode()

Returns the hash code for this BigInteger.

Overrides:

hashCode in class Object

Returns:

hash code for this BigInteger.

See Also:

Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

toString

public String toString(int radix)

Returns the String representation of this BigInteger in the given radix. If the radix is outside the range from Character.MIN_RADIX to Character.MAX_RADIX inclusive, it will default to 10 (as is the case for Integer.toString). The digit-to-character mapping provided by Character.forDigit is used, and a minus sign is prepended if appropriate. (This representation is compatible with the (String, int) constructor.)

Parameters:

radix - radix of the String representation.

Returns:

String representation of this BigInteger in the given radix.

See Also:

Integer.toString(int, int), Character.forDigit(int, int), BigInteger(java.lang.String, int)

toString

public String toString()

Returns the decimal String representation of this BigInteger. The digit-to-character mapping provided by Character.forDigit is used, and a minus sign is prepended if appropriate. (This representation is compatible with the (String) constructor, and allows for String concatenation with Java's + operator.)

Overrides:

toString in class Object

Returns:

decimal String representation of this BigInteger.

See Also:

Character.forDigit(int, int), BigInteger(java.lang.String)

toByteArray

public byte[] toByteArray()

Returns a byte array containing the two's-complement representation of this BigInteger. The byte array will be in big-endian byte-order: the most significant byte is in the zeroth element. The array will contain the minimum number of bytes required to represent this BigInteger, including at least one sign bit, which is (ceil((this.bitLength() + 1)/8)). (This representation is compatible with the (byte[]) constructor.)

Returns:

a byte array containing the two's-complement representation of this BigInteger.

See Also:

BigInteger(byte[])

intValue

public int intValue()

Converts this BigInteger to an int. This conversion is analogous to a narrowing primitive conversion from long to int as defined in The Java™ Language Specification: if this BigInteger is too big to fit in an int, only the low-order 32 bits are returned. Note that this conversion can lose information about the overall magnitude of the BigInteger value as well as return a result with the opposite sign.

Specified by:

intValue in class Number

Returns:

this BigInteger converted to an int.

See Also:

intValueExact()

longValue

public long longValue()

Converts this BigInteger to a long. This conversion is analogous to a narrowing primitive conversion from long to int as defined in The Java™ Language Specification: if this BigInteger is too big to fit in a long, only the low-order 64 bits are returned. Note that this conversion can lose information about the overall magnitude of the BigInteger value as well as return a result with the opposite sign.

Specified by:

longValue in class Number

Returns:

this BigInteger converted to a long.

See Also:

longValueExact()

floatValue

public float floatValue()

Converts this BigInteger to a float. This conversion is similar to the narrowing primitive conversion from double to float as defined in The Java™ Language Specification: if this BigInteger has too great a magnitude to represent as a float, it will be converted to Float.NEGATIVE_INFINITY or Float.POSITIVE_INFINITY as appropriate. Note that even when the return value is finite, this conversion can lose information about the precision of the BigInteger value.

Specified by:

floatValue in class Number

Returns:

this BigInteger converted to a float.

doubleValue

public double doubleValue()

Converts this BigInteger to a double. This conversion is similar to the narrowing primitive conversion from double to float as defined in The Java™ Language Specification: if this BigInteger has too great a magnitude to represent as a double, it will be converted to Double.NEGATIVE_INFINITY or Double.POSITIVE_INFINITY as appropriate. Note that even when the return value is finite, this conversion can lose information about the precision of the BigInteger value.

Specified by:

doubleValue in class Number

Returns:

this BigInteger converted to a double.

longValueExact

public long longValueExact()

Converts this BigInteger to a long, checking for lost information. If the value of this BigInteger is out of the range of the long type, then an ArithmeticException is thrown.

Returns:

this BigInteger converted to a long.

Throws:

ArithmeticException - if the value of this will not exactly fit in a long.

Since:

1.8

See Also:

longValue()

intValueExact

public int intValueExact()

Converts this BigInteger to an int, checking for lost information. If the value of this BigInteger is out of the range of the int type, then an ArithmeticException is thrown.

Returns:

this BigInteger converted to an int.

Throws:

ArithmeticException - if the value of this will not exactly fit in an int.

Since:

1.8

See Also:

intValue()

shortValueExact

public short shortValueExact()

Converts this BigInteger to a short, checking for lost information. If the value of this BigInteger is out of the range of the short type, then an ArithmeticException is thrown.

Returns:

this BigInteger converted to a short.

Throws:

ArithmeticException - if the value of this will not exactly fit in a short.

Since:

1.8

See Also:

Number.shortValue()

byteValueExact

public byte byteValueExact()

Converts this BigInteger to a byte, checking for lost information. If the value of this BigInteger is out of the range of the byte type, then an ArithmeticException is thrown.

Returns:

this BigInteger converted to a byte.

Throws:

ArithmeticException - if the value of this will not exactly fit in a byte.

Since:

1.8

See Also:

Number.byteValue()