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.
Member
, Class
, Class.getMethods()
, Class.getMethod(String, Class[])
, Class.getDeclaredMethods()
, Class.getDeclaredMethod(String, Class[])
DECLARED, PUBLIC
public Class<?> getDeclaringClass()
Returns the Class
object representing the class or interface that declares the executable represented by this object.
getDeclaringClass
in interface Member
getDeclaringClass
in class Executable
public String getName()
Returns the name of the method represented by this Method
object, as a String
.
getName
in interface Member
getName
in class Executable
public int getModifiers()
Returns the Java language modifiers for the executable represented by this object.
getModifiers
in interface Member
getModifiers
in class Executable
Modifier
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.
getTypeParameters
in interface GenericDeclaration
getTypeParameters
in class Executable
TypeVariable
objects that represent the type variables declared by this generic declarationGenericSignatureFormatError
- if the generic signature of this generic declaration does not conform to the format specified in The Java™ Virtual Machine Specification
public Class<?> getReturnType()
Returns a Class
object that represents the formal return type of the method represented by this Method
object.
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.
Type
object that represents the formal return type of the underlying methodGenericSignatureFormatError
- 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 declarationMalformedParameterizedTypeException
- if the underlying method's return typed refers to a parameterized type that cannot be instantiated for any reasonpublic 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.
getParameterTypes
in class Executable
public int getParameterCount()
Returns the number of formal parameters (whether explicitly declared or implicitly declared or neither) for the executable represented by this object.
getParameterCount
in class Executable
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.
getGenericParameterTypes
in class Executable
Type
s that represent the formal parameter types of the underlying executable, in declaration orderGenericSignatureFormatError
- 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 declarationMalformedParameterizedTypeException
- if any of the underlying executable's parameter types refer to a parameterized type that cannot be instantiated for any reasonpublic 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.
getExceptionTypes
in class Executable
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.
getGenericExceptionTypes
in class Executable
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 declarationMalformedParameterizedTypeException
- if the underlying executable's throws
clause refers to a parameterized type that cannot be instantiated for any reasonpublic 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.
equals
in class Object
obj
- the reference object with which to compare.true
if this object is the same as the obj argument; false
otherwise.Object.hashCode()
, HashMap
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.
hashCode
in class Object
Object.equals(java.lang.Object)
, System.identityHashCode(java.lang.Object)
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
.
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
.
toGenericString
in class Executable
Method
, include type parameterspublic 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 fromargs
- the arguments used for the method callobj
with parameters args
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.
public boolean isVarArgs()
Returns true
if this executable was declared to take a variable number of arguments; returns false
otherwise.
isVarArgs
in class Executable
true
if an only if this executable was declared to take a variable number of arguments.public boolean isSynthetic()
Returns true
if this executable is a synthetic construct; returns false
otherwise.
isSynthetic
in interface Member
isSynthetic
in class Executable
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.
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.
Method
instance.TypeNotPresentException
- if the annotation is of type Class
and no definition can be found for the default class value.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.
getAnnotation
in interface AnnotatedElement
getAnnotation
in class Executable
T
- the type of the annotation to query for and return if presentannotationClass
- the Class object corresponding to the annotation typeNullPointerException
- if the given annotation class is nullpublic 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.
getDeclaredAnnotations
in interface AnnotatedElement
getDeclaredAnnotations
in class Executable
public Annotation[][] getParameterAnnotations()
Returns an array of arrays of Annotation
s 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.
getParameterAnnotations
in class Executable
Parameter
, Parameter.getAnnotations()
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.
getAnnotatedReturnType
in class Executable
Executable
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Documentation extracted from Debian's OpenJDK Development Kit package.
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