Class Method
- java.lang.Object
-
- java.lang.reflect.AccessibleObject
-
- java.lang.reflect.Executable
-
- java.lang.reflect.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.
- Since:
- 1.1
- See Also:
-
Member
,Class
,Class.getMethods()
,Class.getMethod(String, Class[])
,Class.getDeclaredMethods()
,Class.getDeclaredMethod(String, Class[])
Field Summary
Fields declared in interface java.lang.reflect.Member
DECLARED, PUBLIC
Method Summary
Modifier and Type | Method | Description |
---|---|---|
boolean | equals(Object obj) | Compares this |
AnnotatedType | getAnnotatedReturnType() | Returns an |
<T extends Annotation> | 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 |
Object | getDefaultValue() | Returns the default value for the annotation member represented by this |
Type[] | getGenericExceptionTypes() | Returns an array of |
Type[] | getGenericParameterTypes() | Returns an array of |
Type | getGenericReturnType() | Returns a |
String | getName() | Returns the name of the method represented by this |
Annotation[][] | getParameterAnnotations() | Returns an array of arrays of |
int | getParameterCount() | Returns the number of formal parameters (whether explicitly declared or implicitly declared or neither) for the executable represented by this object. |
Class<?> | getReturnType() | Returns a |
TypeVariable<Method>[] | getTypeParameters() | Returns an array of |
int | hashCode() | Returns a hashcode for this |
Object | invoke(Object obj,
Object... args) | Invokes the underlying method represented by this |
boolean | isBridge() | Returns |
boolean | isDefault() | Returns |
boolean | isSynthetic() | Returns |
boolean | isVarArgs() | Returns |
void | setAccessible(boolean flag) | Set the |
String | toGenericString() | Returns a string describing this |
String | toString() | Returns a string describing this |
Methods declared in class java.lang.reflect.Executable
getAnnotatedExceptionTypes, getAnnotatedParameterTypes, getAnnotatedReceiverType, getAnnotationsByType, getExceptionTypes, getModifiers, getParameters, getParameterTypes
Methods declared in class java.lang.reflect.AccessibleObject
canAccess, getAnnotations, getDeclaredAnnotation, getDeclaredAnnotationsByType, isAccessible, isAnnotationPresent, setAccessible, trySetAccessible
Methods declared in class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
Methods declared in interface java.lang.reflect.AnnotatedElement
getAnnotations, getDeclaredAnnotation, getDeclaredAnnotationsByType, isAnnotationPresent
Method Detail
setAccessible
public void setAccessible(boolean flag)
Description copied from class: AccessibleObject
Set the accessible
flag for this reflected object to the indicated boolean value. A value of true
indicates that the reflected object should suppress checks for Java language access control when it is used. A value of false
indicates that the reflected object should enforce checks for Java language access control when it is used, with the variation noted in the class description.
This method may be used by a caller in class C
to enable access to a member
of declaring class
D
if any of the following hold:
-
C
andD
are in the same module. - The member is
public
andD
ispublic
in a package that the module containingD
exports
to at least the module containingC
. - The member is
protected
static
,D
ispublic
in a package that the module containingD
exports to at least the module containingC
, andC
is a subclass ofD
. -
D
is in a package that the module containingD
opens
to at least the module containingC
. All packages in unnamed and open modules are open to all modules and so this method always succeeds whenD
is in an unnamed or open module.
This method cannot be used to enable access to private members, members with default (package) access, protected instance members, or protected constructors when the declaring class is in a different module to the caller and the package containing the declaring class is not open to the caller's module.
If there is a security manager, its checkPermission
method is first called with a ReflectPermission("suppressAccessChecks")
permission.
- Overrides:
-
setAccessible
in classAccessibleObject
- Parameters:
-
flag
- the new value for theaccessible
flag - Throws:
-
InaccessibleObjectException
- if access cannot be enabled -
SecurityException
- if the request is denied by the security manager - See Also:
-
AccessibleObject.trySetAccessible()
,MethodHandles.privateLookupIn(java.lang.Class<?>, java.lang.invoke.MethodHandles.Lookup)
getDeclaringClass
public Class<?> getDeclaringClass()
Returns the Class
object representing the class or interface that declares the method represented by this object.
- Specified by:
-
getDeclaringClass
in interfaceMember
- Specified by:
-
getDeclaringClass
in classExecutable
- 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 interfaceMember
- Specified by:
-
getName
in classExecutable
- Returns:
- the simple name of the underlying member
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 interfaceGenericDeclaration
- Specified by:
-
getTypeParameters
in classExecutable
- 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
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 classExecutable
- 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 classExecutable
- Returns:
- an array of
Type
s 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
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 classExecutable
- 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'sthrows
clause refers to a non-existent type declaration -
MalformedParameterizedTypeException
- if the underlying executable'sthrows
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 classObject
- 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 classObject
- 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
.
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 classExecutable
- 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, section 15.12.4.4; in particular, overriding based on the runtime type of the target object may 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 parametersargs
- Throws:
-
IllegalAccessException
- if thisMethod
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 classExecutable
- 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 interfaceMember
- Overrides:
-
isSynthetic
in classExecutable
- 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 typeClass
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 interfaceAnnotatedElement
- Overrides:
-
getAnnotation
in classExecutable
- 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 interfaceAnnotatedElement
- Overrides:
-
getDeclaredAnnotations
in classAccessibleObject
- Returns:
- annotations directly present on this element
- Since:
- 1.5
getParameterAnnotations
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.
- Specified by:
-
getParameterAnnotations
in classExecutable
- 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
,AnnotatedElement.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 classExecutable
- Returns:
- an object representing the return type of the method or constructor represented by this
Executable
- Since:
- 1.8