Class Method

All Implemented Interfaces:
AnnotatedElement, GenericDeclaration, Member 

public final class Method
extends Executable

A Method provides information about, and access to, a single method on a class or interface. The reflected method may be a class method or an instance method (including an abstract method).

A Method permits widening conversions to occur when matching the actual parameters to invoke with the underlying method's formal parameters, but it throws an IllegalArgumentException if a narrowing conversion would occur.

See Also:
Member, Class, Class.getMethods(), Class.getMethod(String, Class[]), Class.getDeclaredMethods(), Class.getDeclaredMethod(String, Class[])

Fields

Fields inherited from interface java.lang.reflect.Member

DECLARED, PUBLIC

Methods

Modifier and Type Method and Description
boolean equals(Object obj)

Compares this Method against the specified object.
AnnotatedType getAnnotatedReturnType()

Returns an AnnotatedType object that represents the use of a type to specify the return type of the method/constructor represented by this Executable.
<T extends Annotation>
T		 getAnnotation(Class<T> annotationClass)

Returns this element's annotation for the specified type if such an annotation is present, else null.
Annotation[] getDeclaredAnnotations()

Returns annotations that are directly present on this element.
Class<?> getDeclaringClass()

Returns the Class object representing the class or interface that declares the executable represented by this object.
Object getDefaultValue()

Returns the default value for the annotation member represented by this Method instance.
Class<?>[] getExceptionTypes()

Returns an array of Class objects that represent the types of exceptions declared to be thrown by the underlying executable represented by this object.
Type[] getGenericExceptionTypes()

Returns an array of Type objects that represent the exceptions declared to be thrown by this executable object.
Type[] getGenericParameterTypes()

Returns an array of Type objects that represent the formal parameter types, in declaration order, of the executable represented by this object.
Type getGenericReturnType()

Returns a Type object that represents the formal return type of the method represented by this Method object.
int getModifiers()

Returns the Java language modifiers for the executable represented by this object.
String getName()

Returns the name of the method represented by this Method object, as a String.
Annotation[][] getParameterAnnotations()

Returns an array of arrays of Annotations that represent the annotations on the formal parameters, in declaration order, of the Executable represented by this object.
int getParameterCount()

Returns the number of formal parameters (whether explicitly declared or implicitly declared or neither) for the executable represented by this object.
Class<?>[] getParameterTypes()

Returns an array of Class objects that represent the formal parameter types, in declaration order, of the executable represented by this object.
Class<?> getReturnType()

Returns a Class object that represents the formal return type of the method represented by this Method object.
TypeVariable<Method>[] getTypeParameters()

Returns an array of TypeVariable objects that represent the type variables declared by the generic declaration represented by this GenericDeclaration object, in declaration order.
int hashCode()

Returns a hashcode for this Method.
Object invoke(Object obj, Object... args)

Invokes the underlying method represented by this Method object, on the specified object with the specified parameters.
boolean isBridge()

Returns true if this method is a bridge method; returns false otherwise.
boolean isDefault()

Returns true if this method is a default method; returns false otherwise.
boolean isSynthetic()

Returns true if this executable is a synthetic construct; returns false otherwise.
boolean isVarArgs()

Returns true if this executable was declared to take a variable number of arguments; returns false otherwise.
String toGenericString()

Returns a string describing this Method, including type parameters.
String toString()

Returns a string describing this Method.

Methods inherited from class java.lang.reflect.Executable

getAnnotatedExceptionTypes, getAnnotatedParameterTypes, getAnnotatedReceiverType, getAnnotationsByType, getParameters

Methods inherited from class java.lang.reflect.AccessibleObject

getAnnotations, getDeclaredAnnotation, getDeclaredAnnotationsByType, isAccessible, isAnnotationPresent, setAccessible, setAccessible

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.lang.reflect.AnnotatedElement

getAnnotations, getDeclaredAnnotation, getDeclaredAnnotationsByType, isAnnotationPresent

Methods

getDeclaringClass

public Class<?> getDeclaringClass()

Returns the Class object representing the class or interface that declares the executable represented by this object.

Specified by:
getDeclaringClass in interface Member
Specified by:
getDeclaringClass in class Executable
Returns:
an object representing the declaring class of the underlying member

getName

public String getName()

Returns the name of the method represented by this Method object, as a String.

Specified by:
getName in interface Member
Specified by:
getName in class Executable
Returns:
the simple name of the underlying member

getModifiers

public int getModifiers()

Returns the Java language modifiers for the executable represented by this object.

Specified by:
getModifiers in interface Member
Specified by:
getModifiers in class Executable
Returns:
the Java language modifiers for the underlying member
See Also:
Modifier

getTypeParameters

public TypeVariable<Method>[] getTypeParameters()

Returns an array of TypeVariable objects that represent the type variables declared by the generic declaration represented by this GenericDeclaration object, in declaration order. Returns an array of length 0 if the underlying generic declaration declares no type variables.

Specified by:
getTypeParameters in interface GenericDeclaration
Specified by:
getTypeParameters in class Executable
Returns:
an array of TypeVariable objects that represent the type variables declared by this generic declaration
Throws:
GenericSignatureFormatError - if the generic signature of this generic declaration does not conform to the format specified in The Java™ Virtual Machine Specification
Since:
1.5

getReturnType

public Class<?> getReturnType()

Returns a Class object that represents the formal return type of the method represented by this Method object.

Returns:
the return type for the method this object represents

getGenericReturnType

public Type getGenericReturnType()

Returns a Type object that represents the formal return type of the method represented by this Method object.

If the return type is a parameterized type, the Type object returned must accurately reflect the actual type parameters used in the source code.

If the return type is a type variable or a parameterized type, it is created. Otherwise, it is resolved.

Returns:
a Type object that represents the formal return type of the underlying method
Throws:
GenericSignatureFormatError - if the generic method signature does not conform to the format specified in The Java™ Virtual Machine Specification
TypeNotPresentException - if the underlying method's return type refers to a non-existent type declaration
MalformedParameterizedTypeException - if the underlying method's return typed refers to a parameterized type that cannot be instantiated for any reason
Since:
1.5

getParameterTypes

public Class<?>[] getParameterTypes()

Returns an array of Class objects that represent the formal parameter types, in declaration order, of the executable represented by this object. Returns an array of length 0 if the underlying executable takes no parameters.

Specified by:
getParameterTypes in class Executable
Returns:
the parameter types for the executable this object represents

getParameterCount

public int getParameterCount()

Returns the number of formal parameters (whether explicitly declared or implicitly declared or neither) for the executable represented by this object.

Overrides:
getParameterCount in class Executable
Returns:
The number of formal parameters for the executable this object represents
Since:
1.8

getGenericParameterTypes

public Type[] getGenericParameterTypes()

Returns an array of Type objects that represent the formal parameter types, in declaration order, of the executable represented by this object. Returns an array of length 0 if the underlying executable takes no parameters.

If a formal parameter type is a parameterized type, the Type object returned for it must accurately reflect the actual type parameters used in the source code.

If a formal parameter type is a type variable or a parameterized type, it is created. Otherwise, it is resolved.

Overrides:
getGenericParameterTypes in class Executable
Returns:
an array of Types that represent the formal parameter types of the underlying executable, in declaration order
Throws:
GenericSignatureFormatError - if the generic method signature does not conform to the format specified in The Java™ Virtual Machine Specification
TypeNotPresentException - if any of the parameter types of the underlying executable refers to a non-existent type declaration
MalformedParameterizedTypeException - if any of the underlying executable's parameter types refer to a parameterized type that cannot be instantiated for any reason
Since:
1.5

getExceptionTypes

public Class<?>[] getExceptionTypes()

Returns an array of Class objects that represent the types of exceptions declared to be thrown by the underlying executable represented by this object. Returns an array of length 0 if the executable declares no exceptions in its throws clause.

Specified by:
getExceptionTypes in class Executable
Returns:
the exception types declared as being thrown by the executable this object represents

getGenericExceptionTypes

public Type[] getGenericExceptionTypes()

Returns an array of Type objects that represent the exceptions declared to be thrown by this executable object. Returns an array of length 0 if the underlying executable declares no exceptions in its throws clause.

If an exception type is a type variable or a parameterized type, it is created. Otherwise, it is resolved.

Overrides:
getGenericExceptionTypes in class Executable
Returns:
an array of Types that represent the exception types thrown by the underlying executable
Throws:
GenericSignatureFormatError - if the generic method signature does not conform to the format specified in The Java™ Virtual Machine Specification
TypeNotPresentException - if the underlying executable's throws clause refers to a non-existent type declaration
MalformedParameterizedTypeException - if the underlying executable's throws clause refers to a parameterized type that cannot be instantiated for any reason
Since:
1.5

equals

public boolean equals(Object obj)

Compares this Method against the specified object. Returns true if the objects are the same. Two Methods are the same if they were declared by the same class and have the same name and formal parameter types and return type.

Overrides:
equals in class Object
Parameters:
obj - the reference object with which to compare.
Returns:
true if this object is the same as the obj argument; false otherwise.
See Also:
Object.hashCode(), HashMap

hashCode

public int hashCode()

Returns a hashcode for this Method. The hashcode is computed as the exclusive-or of the hashcodes for the underlying method's declaring class name and the method's name.

Overrides:
hashCode in class Object
Returns:
a hash code value for this object.
See Also:
Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

toString

public String toString()

Returns a string describing this Method. The string is formatted as the method access modifiers, if any, followed by the method return type, followed by a space, followed by the class declaring the method, followed by a period, followed by the method name, followed by a parenthesized, comma-separated list of the method's formal parameter types. If the method throws checked exceptions, the parameter list is followed by a space, followed by the word throws followed by a comma-separated list of the thrown exception types. For example: 

public boolean java.lang.Object.equals(java.lang.Object)

The access modifiers are placed in canonical order as specified by "The Java Language Specification". This is public, protected or private first, and then other modifiers in the following order: abstract, default, static, final, synchronized, native, strictfp.

Overrides:
toString in class Object
Returns:
a string describing this Method

toGenericString

public String toGenericString()

Returns a string describing this Method, including type parameters. The string is formatted as the method access modifiers, if any, followed by an angle-bracketed comma-separated list of the method's type parameters, if any, followed by the method's generic return type, followed by a space, followed by the class declaring the method, followed by a period, followed by the method name, followed by a parenthesized, comma-separated list of the method's generic formal parameter types. If this method was declared to take a variable number of arguments, instead of denoting the last parameter as "Type[]", it is denoted as "Type...". A space is used to separate access modifiers from one another and from the type parameters or return type. If there are no type parameters, the type parameter list is elided; if the type parameter list is present, a space separates the list from the class name. If the method is declared to throw exceptions, the parameter list is followed by a space, followed by the word throws followed by a comma-separated list of the generic thrown exception types.

The access modifiers are placed in canonical order as specified by "The Java Language Specification". This is public, protected or private first, and then other modifiers in the following order: abstract, default, static, final, synchronized, native, strictfp.

Specified by:
toGenericString in class Executable
Returns:
a string describing this Method, include type parameters
Since:
1.5

invoke

public Object invoke(Object obj,
                     Object... args)
              throws IllegalAccessException,
                     IllegalArgumentException,
                     InvocationTargetException

Invokes the underlying method represented by this Method object, on the specified object with the specified parameters. Individual parameters are automatically unwrapped to match primitive formal parameters, and both primitive and reference parameters are subject to method invocation conversions as necessary.

If the underlying method is static, then the specified obj argument is ignored. It may be null.

If the number of formal parameters required by the underlying method is 0, the supplied args array may be of length 0 or null.

If the underlying method is an instance method, it is invoked using dynamic method lookup as documented in The Java Language Specification, Second Edition, section 15.12.4.4; in particular, overriding based on the runtime type of the target object will occur.

If the underlying method is static, the class that declared the method is initialized if it has not already been initialized.

If the method completes normally, the value it returns is returned to the caller of invoke; if the value has a primitive type, it is first appropriately wrapped in an object. However, if the value has the type of an array of a primitive type, the elements of the array are not wrapped in objects; in other words, an array of primitive type is returned. If the underlying method return type is void, the invocation returns null.

Parameters:
obj - the object the underlying method is invoked from
args - the arguments used for the method call
Returns:
the result of dispatching the method represented by this object on obj with parameters args
Throws:
IllegalAccessException - if this Method object is enforcing Java language access control and the underlying method is inaccessible.
IllegalArgumentException - if the method is an instance method and the specified object argument is not an instance of the class or interface declaring the underlying method (or of a subclass or implementor thereof); if the number of actual and formal parameters differ; if an unwrapping conversion for primitive arguments fails; or if, after possible unwrapping, a parameter value cannot be converted to the corresponding formal parameter type by a method invocation conversion.
InvocationTargetException - if the underlying method throws an exception.
NullPointerException - if the specified object is null and the method is an instance method.
ExceptionInInitializerError - if the initialization provoked by this method fails.

isBridge

public boolean isBridge()

Returns true if this method is a bridge method; returns false otherwise.

Returns:
true if and only if this method is a bridge method as defined by the Java Language Specification.
Since:
1.5

isVarArgs

public boolean isVarArgs()

Returns true if this executable was declared to take a variable number of arguments; returns false otherwise.

Overrides:
isVarArgs in class Executable
Returns:
true if an only if this executable was declared to take a variable number of arguments.
Since:
1.5

isSynthetic

public boolean isSynthetic()

Returns true if this executable is a synthetic construct; returns false otherwise.

Specified by:
isSynthetic in interface Member
Overrides:
isSynthetic in class Executable
Returns:
true if and only if this executable is a synthetic construct as defined by The Java™ Language Specification.
Since:
1.5

isDefault

public boolean isDefault()

Returns true if this method is a default method; returns false otherwise. A default method is a public non-abstract instance method, that is, a non-static method with a body, declared in an interface type.

Returns:
true if and only if this method is a default method as defined by the Java Language Specification.
Since:
1.8

getDefaultValue

public Object getDefaultValue()

Returns the default value for the annotation member represented by this Method instance. If the member is of a primitive type, an instance of the corresponding wrapper type is returned. Returns null if no default is associated with the member, or if the method instance does not represent a declared member of an annotation type.

Returns:
the default value for the annotation member represented by this Method instance.
Throws:
TypeNotPresentException - if the annotation is of type Class and no definition can be found for the default class value.
Since:
1.5

getAnnotation

public <T extends Annotation> T getAnnotation(Class<T> annotationClass)

Returns this element's annotation for the specified type if such an annotation is present, else null.

Specified by:
getAnnotation in interface AnnotatedElement
Overrides:
getAnnotation in class Executable
Type Parameters:
T - the type of the annotation to query for and return if present
Parameters:
annotationClass - the Class object corresponding to the annotation type
Returns:
this element's annotation for the specified annotation type if present on this element, else null
Throws:
NullPointerException - if the given annotation class is null
Since:
1.5

getDeclaredAnnotations

public Annotation[] getDeclaredAnnotations()

Returns annotations that are directly present on this element. This method ignores inherited annotations. If there are no annotations directly present on this element, the return value is an array of length 0. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.

Specified by:
getDeclaredAnnotations in interface AnnotatedElement
Overrides:
getDeclaredAnnotations in class Executable
Returns:
annotations directly present on this element
Since:
1.5

getParameterAnnotations

public Annotation[][] getParameterAnnotations()

Returns an array of arrays of Annotations that represent the annotations on the formal parameters, in declaration order, of the Executable represented by this object. Synthetic and mandated parameters (see explanation below), such as the outer "this" parameter to an inner class constructor will be represented in the returned array. If the executable has no parameters (meaning no formal, no synthetic, and no mandated parameters), a zero-length array will be returned. If the Executable has one or more parameters, a nested array of length zero is returned for each parameter with no annotations. The annotation objects contained in the returned arrays are serializable. The caller of this method is free to modify the returned arrays; it will have no effect on the arrays returned to other callers. A compiler may add extra parameters that are implicitly declared in source ("mandated"), as well as parameters that are neither implicitly nor explicitly declared in source ("synthetic") to the parameter list for a method. See Parameter for more information.

Specified by:
getParameterAnnotations in class Executable
Returns:
an array of arrays that represent the annotations on the formal and implicit parameters, in declaration order, of the executable represented by this object
Since:
1.5
See Also:
Parameter, Parameter.getAnnotations()

getAnnotatedReturnType

public AnnotatedType getAnnotatedReturnType()

Returns an AnnotatedType object that represents the use of a type to specify the return type of the method/constructor represented by this Executable. If this Executable object represents a constructor, the AnnotatedType object represents the type of the constructed object. If this Executable object represents a method, the AnnotatedType object represents the use of a type to specify the return type of the method.

Specified by:
getAnnotatedReturnType in class Executable
Returns:
an object representing the return type of the method or constructor represented by this Executable
Since:
1.8

© 1993, 2020, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Method.html