Java™ Platform
Standard Ed. 6

java.lang.reflect
Class Method

java.lang.Object
  extended by java.lang.reflect.AccessibleObject
      extended by java.lang.reflect.Method
All Implemented Interfaces:
AnnotatedElement, GenericDeclaration, Member

public final class Method
extends AccessibleObject
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:
Member, Class, Class.getMethods(), Class.getMethod(String, Class[]), Class.getDeclaredMethods(), Class.getDeclaredMethod(String, Class[])

Field Summary
 
Fields inherited from interface java.lang.reflect.Member
DECLARED, PUBLIC
 
Method Summary
 boolean equals(Object obj)
          Compares this Method against the specified object.
<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 all annotations that are directly present on this element.
 Class<?> getDeclaringClass()
          Returns the Class object representing the class or interface that declares the method represented by this Method 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 the exceptions declared to be thrown by the underlying method represented by this Method object.
 Type[] getGenericExceptionTypes()
          Returns an array of Type objects that represent the exceptions declared to be thrown by this Method object.
 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.
 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 method represented by this Method object, as an integer.
 String getName()
          Returns the name of the method represented by this Method object, as a String.
 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.
 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.
 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 isSynthetic()
          Returns true if this method is a synthetic method; returns false otherwise.
 boolean isVarArgs()
          Returns true if this method 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.AccessibleObject
getAnnotations, isAccessible, isAnnotationPresent, setAccessible, setAccessible
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Method Detail

getDeclaringClass

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

Specified by:
getDeclaringClass in interface Member
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
Returns:
the simple name of the underlying member

getModifiers

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.

Specified by:
getModifiers in interface Member
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
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, 3rd edition
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, 3rd edition
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 method represented by this Method object. Returns an array of length 0 if the underlying method takes no parameters.

Returns:
the parameter types for the method this object represents

getGenericParameterTypes

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.

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

getExceptionTypes

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.

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

getGenericExceptionTypes

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.

Returns:
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
TypeNotPresentException - if the underlying method's throws clause refers to a non-existent type declaration
MalformedParameterizedTypeException - if the underlying method'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(), Hashtable

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), Hashtable

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, static, final, synchronized, native.

Overrides:
toString in class Object
Returns:
a string representation of the object.

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. 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.

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 enforces 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 method was declared to take a variable number of arguments; returns false otherwise.

Returns:
true if an only if this method was declared to take a variable number of arguments.
Since:
1.5

isSynthetic

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

Specified by:
isSynthetic in interface Member
Returns:
true if and only if this method is a synthetic method as defined by the Java Language Specification.
Since:
1.5

getAnnotation

public <T extends Annotation> T getAnnotation(Class<T> annotationClass)
Description copied from interface: AnnotatedElement
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 AccessibleObject
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()
Description copied from interface: AnnotatedElement
Returns all annotations that are directly present on this element. Unlike the other methods in this interface, this method ignores inherited annotations. (Returns an array of length zero if no annotations are directly present on this element.) 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 AccessibleObject
Returns:
All annotations directly present on this element
Since:
1.5

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

getParameterAnnotations

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.

Returns:
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

Java™ Platform
Standard Ed. 6

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