java.lang.reflect.Method

Method

Java SE 6

Implements: GenericDeclaration, Member

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 java.lang.reflect.Member, java.lang.Class, getMethods(), getMethod(String, Class[]), getDeclaredMethods(), getDeclaredMethod(String, Class[])

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.

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.

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.

obj the object the underlying method is invoked from

args the arguments used for the method call

return the result of dispatching the method represented by this object on obj with parameters args

Throws IllegalAccessException: if this Method object enforces Java language access control and the underlying method is inaccessible.

Throws 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.

Throws InvocationTargetException: if the underlying method throws an exception.

Throws NullPointerException: if the specified object is null and the method is an instance method.

Throws ExceptionInInitializerError: if the initialization provoked by this method fails.

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. 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. If there are no type parameters, the type parameter list is elided.

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, static, final, synchronized native.

return a string describing this Method, include type parameters

since 1.5

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)

Properties

public Annotation<T>

getAnnotation(Class annotationClass)

Throws	NullPointerException: if the given annotation class is null
since	1.5

public boolean

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

return	true if and only if this method is a bridge method as defined by the Java Language Specification.
since	1.5

public Annotation[]

getDeclaredAnnotations()

since

1.5

public Class

getDeclaringClass()
Returns the Class object representing the class or interface that declares the method represented by this Method object.

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.

return	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

public Class[]

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

return

the exception types declared as being thrown by the method this object represents

public Type[]

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

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

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

return an array of Types that represent the exception types thrown by the underlying method

Throws GenericSignatureFormatError: if the generic method signature does not conform to the format specified in the Java Virtual Machine Specification, 3rd edition

Throws TypeNotPresentException: if the underlying method's throws clause refers to a non-existent type declaration

Throws MalformedParameterizedTypeException: if the underlying method's throws clause refers to a parameterized type that cannot be instantiated for any reason

since 1.5

public Type[]

getGenericParameterTypes()
Returns an array of Type objects that represent the formal parameter types, in declaration order, of the method represented by this Method object. Returns an array of length 0 if the underlying method 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.

return an array of Types that represent the formal parameter types of the underlying method, in declaration order

Throws GenericSignatureFormatError: if the generic method signature does not conform to the format specified in the Java Virtual Machine Specification, 3rd edition

Throws TypeNotPresentException: if any of the parameter types of the underlying method refers to a non-existent type declaration

Throws MalformedParameterizedTypeException: if any of the underlying method's parameter types refer to a parameterized type that cannot be instantiated for any reason

since 1.5

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.

return 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, 3rd edition

Throws TypeNotPresentException: if the underlying method's return type refers to a non-existent type declaration

Throws MalformedParameterizedTypeException: if the underlying method's return typed refers to a parameterized type that cannot be instantiated for any reason

since 1.5

public int

getModifiers()
Returns the Java language modifiers for the method represented by this Method object, as an integer. The Modifier class should be used to decode the modifiers.

See also

java.lang.reflect.Modifier

public String

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

public Annotation[][]

getParameterAnnotations()
Returns an array of arrays that represent the annotations on the formal parameters, in declaration order, of the method represented by this Method object. (Returns an array of length zero if the underlying method is parameterless. If the method 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.

return	an array of arrays that represent the annotations on the formal parameters, in declaration order, of the method represented by this Method object
since	1.5

public Class[]

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

return

the parameter types for the method this object represents

public Class

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

return

the return type for the method this object represents

public boolean

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

return	true if and only if this method is a synthetic method as defined by the Java Language Specification.
since	1.5

public 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. Returns an array of length 0 if the underlying generic declaration declares no type variables.

return	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, 3rd edition
since	1.5

public boolean

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

return	`true` if an only if this method was declared to take a variable number of arguments.
since	1.5

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Java SE 6