Method

AI-generated Key Takeaways

• The Method class in Java's reflection API provides information about and access to methods, including their invocation, parameters, and return types.

• It supports widening conversions for parameter matching but throws exceptions for narrowing conversions.

• Method allows retrieval of method metadata like name, modifiers, annotations, and exceptions.

• The class facilitates dynamic interaction with methods for tasks like introspection and runtime manipulation.

• Both toGenericString() and toString() provide string representations of a method, with the former including generic type information.

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[])

Inherited Constant Summary

From interface java.lang.reflect.Member

int	DECLARED	Identifies the set of declared members of a class or interface.
int	PUBLIC	Identifies the set of all public members of a class or interface, including inherited members.

Public Method Summary

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 {@linkplain Modifier 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.

Inherited Method Summary

From class java.lang.reflect.Executable

AnnotatedType[]	getAnnotatedExceptionTypes() Returns an array of AnnotatedType objects that represent the use of types to specify the declared exceptions of the method/constructor represented by this Executable.
AnnotatedType[]	getAnnotatedParameterTypes() Returns an array of AnnotatedType objects that represent the use of types to specify formal parameter types of the method/constructor represented by this Executable.
AnnotatedType	getAnnotatedReceiverType() Returns an AnnotatedType object that represents the use of a type to specify the receiver type of the method/constructor represented by this Executable object.
abstract 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> cls) Returns this element's annotation for the specified type if such an annotation is present, else null.
<T extends Annotation> T[]	getAnnotationsByType(Class<T> cls) Returns annotations that are associated with this element.
Annotation[]	getDeclaredAnnotations() Returns annotations that are directly present on this element.
abstract Class<?>	getDeclaringClass() Returns the Class object representing the class or interface that declares the executable represented by this object.
abstract 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.
abstract int	getModifiers() Returns the Java language {@linkplain Modifier modifiers} for the executable represented by this object.
abstract String	getName() Returns the name of the executable represented by this object.
abstract 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.
abstract Class[]<?>	getParameterTypes() Returns an array of Class objects that represent the formal parameter types, in declaration order, of the executable represented by this object.
Parameter[]	getParameters() Returns an array of Parameter objects that represent all the parameters to the underlying executable represented by this object.
abstract TypeVariable[]<?>	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.
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.
abstract String	toGenericString() Returns a string describing this Executable, including any type parameters.

From class java.lang.reflect.AccessibleObject

<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[]	getAnnotations() Returns annotations that are present on this element.
<T extends Annotation> T[]	getAnnotationsByType(Class<T> annotationClass) Returns annotations that are associated with this element.
<T extends Annotation> T	getDeclaredAnnotation(Class<T> annotationClass) Returns this element's annotation for the specified type if such an annotation is directly present, else null.
Annotation[]	getDeclaredAnnotations() Returns annotations that are directly present on this element.
<T extends Annotation> T[]	getDeclaredAnnotationsByType(Class<T> annotationClass) Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present.
boolean	isAccessible() Get the value of the accessible flag for this object.
boolean	isAnnotationPresent(Class<? extends Annotation> annotationClass) Returns true if an annotation for the specified type is present on this element, else false.
void	setAccessible(boolean flag) Set the accessible flag for this object to the indicated boolean value.
static void	setAccessible(AccessibleObject[] array, boolean flag) Convenience method to set the accessible flag for an array of objects with a single security check (for efficiency).

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.lang.reflect.Member

abstract Class<?>	getDeclaringClass() Returns the Class object representing the class or interface that declares the member or constructor represented by this Member.
abstract int	getModifiers() Returns the Java language modifiers for the member or constructor represented by this Member, as an integer.
abstract String	getName() Returns the simple name of the underlying member or constructor represented by this Member.
abstract boolean	isSynthetic() Returns true if this member was introduced by the compiler; returns false otherwise.

From interface java.lang.reflect.GenericDeclaration

abstract TypeVariable[]<?>

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.

From interface java.lang.reflect.AnnotatedElement

abstract <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.
abstract Annotation[]	getAnnotations() Returns annotations that are present on this element.
<T extends Annotation> T[]	getAnnotationsByType(Class<T> annotationClass) Returns annotations that are associated with this element.
<T extends Annotation> T	getDeclaredAnnotation(Class<T> annotationClass) Returns this element's annotation for the specified type if such an annotation is directly present, else null.
abstract Annotation[]	getDeclaredAnnotations() Returns annotations that are directly present on this element.
<T extends Annotation> T[]	getDeclaredAnnotationsByType(Class<T> annotationClass) Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present.
boolean	isAnnotationPresent(Class<? extends Annotation> annotationClass) Returns true if an annotation for the specified type is present on this element, else false.

Public Methods

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.

Parameters

obj	the object to compare this instance with.

Returns

• true if the specified object is equal to this Object; false otherwise.

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.

Returns

• an object representing the return type of the method or constructor represented by this Executable

public T getAnnotation (Class<T> annotationClass)

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

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

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.

Returns

• annotations directly present on this element

public Class<?> getDeclaringClass ()

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

Returns

• an object representing the declaring class of the underlying member

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.

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.

Returns

• the exception types declared as being thrown by the executable this object represents

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.

Returns

• an array of Types that represent the exception types thrown by the underlying executable

Throws

GenericSignatureFormatError
TypeNotPresentException
MalformedParameterizedTypeException

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.

Returns

• an array of Types that represent the formal parameter types of the underlying executable, in declaration order

Throws

GenericSignatureFormatError
TypeNotPresentException
MalformedParameterizedTypeException

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

public int getModifiers ()

Returns the Java language {@linkplain Modifier modifiers} for the executable represented by this object.

Returns

• the Java language modifiers for the underlying member

public String getName ()

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

Returns

• the simple name of the underlying member

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.

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

public int getParameterCount ()

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

Returns

• The number of formal parameters for the executable this object represents

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.

Returns

• the parameter types for the executable this object represents

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

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.

Returns

• an array of TypeVariable objects that represent the type variables declared by this generic declaration

Throws

GenericSignatureFormatError

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.

Returns

• this object's hash code.

public Object invoke (Object obj, Object... args)

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.

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.

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.

public boolean isSynthetic ()

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

Returns

• true if and only if this executable is a synthetic construct as defined by The Java™ Language Specification.

public boolean isVarArgs ()

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

Returns

• true if an only if this executable was declared to take a variable number of arguments.

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.

Returns

• a string describing this Method, include type parameters

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.

Returns

• a string describing this Method