Method (Java SE 11 & JDK 11 )
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Method
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Method
 
Module java.base
Package java.lang.reflect
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
All Methods Instance Methods Concrete Methods 
Modifier and Type
Method
Description
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 method represented by this object.
Object
getDefaultValue()
Returns the default value for the annotation member represented by
this Method instance.
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.
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<?>
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.
void
setAccessible​(boolean flag)
Set the accessible flag for this reflected object to
the indicated boolean value.
String
toGenericString()
Returns a string describing this Method, including
type parameters.
String
toString()
Returns a string describing this Method.
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 and D are in the same module.
The member is public and D is public in
a package that the module containing D exports to at least the module
containing C.
The member is protected static, D is
public in a package that the module containing D
exports to at least the module containing C, and C
is a subclass of D.
D is in a package that the module containing D
opens to at least the module
containing C.
All packages in unnamed and open modules are open to all modules and
so this method always succeeds when D 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 class AccessibleObject
Parameters:
flag - the new value for the accessible 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 interface Member
Specified by:
getDeclaringClass in class Executable
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
Specified by:
getName in class Executable
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 interface GenericDeclaration
Specified by:
getTypeParameters in class Executable
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 class Executable
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 class Executable
Returns:
an array of Types 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 class Executable
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's
throws clause refers to a non-existent type declaration
MalformedParameterizedTypeException - if
the underlying executable'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(),
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 class Object
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.
Overrides:
toString in class Object
Returns:
a string describing this Method
See The Java™ Language Specification:
8.4.3 Method Modifiers, 9.4   Method Declarations, 9.6.1 Annotation Type Elements
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 class Executable
Returns:
a string describing this Method,
include type parameters
Since:
1.5
See The Java™ Language Specification:
8.4.3 Method Modifiers, 9.4   Method Declarations, 9.6.1 Annotation Type Elements
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 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.
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 class Executable
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 interface Member
Overrides:
isSynthetic in class Executable
Returns:
true if and only if this executable is a synthetic
construct as defined by
The Java™ Language Specification.
Since:
1.5
See The Java™ Language Specification:
13.1 The Form of a Binary
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 type
Class 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 interface AnnotatedElement
Overrides:
getAnnotation in class Executable
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 interface AnnotatedElement
Overrides:
getDeclaredAnnotations in class AccessibleObject
Returns:
annotations directly present on this element
Since:
1.5
getParameterAnnotations
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.
Specified by:
getParameterAnnotations in class Executable
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 class Executable
Returns:
an object representing the return type of the method
or constructor represented by this Executable
Since:
1.8
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