Module java.base

Package java.lang.reflect

Class Parameter

java.lang.Object

java.lang.reflect.Parameter

All Implemented Interfaces:

AnnotatedElement

public final class Parameter
extends Object
implements AnnotatedElement

Information about method parameters. A Parameter provides information about method parameters, including its name and modifiers. It also provides an alternate means of obtaining attributes for the parameter.

Since:

1.8

Method Summary

Modifier and Type	Method	Description
Set<AccessFlag>	accessFlags()	Returns an unmodifiable set of the access flags for the parameter represented by this object, possibly empty.
boolean	equals(Object obj)	Compares based on the executable and the index.
AnnotatedType	getAnnotatedType()	Returns an AnnotatedType object that represents the use of a type to specify the type of the formal parameter represented by this Parameter.
<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[]	getAnnotations()	Returns annotations that are present on this element.
<T extends Annotation> T[]	getAnnotationsByType(Class<T> annotationClass)	Returns annotations that are associated with this element.
<T extends Annotation> T	getDeclaredAnnotation(Class<T> annotationClass)	Returns this element's annotation for the specified type if such an annotation is directly present, else null.
Annotation[]	getDeclaredAnnotations()	Returns annotations that are directly present on this element.
<T extends Annotation> T[]	getDeclaredAnnotationsByType(Class<T> annotationClass)	Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present.
Executable	getDeclaringExecutable()	Returns the Executable declaring this parameter.
int	getModifiers()	Returns the Java language modifiers for the parameter represented by this object.
String	getName()	Returns the name of the parameter.
Type	getParameterizedType()	Returns a Type object that identifies the parameterized type for the parameter represented by this Parameter object.
Class<?>	getType()	Returns a Class object that identifies the declared type for the parameter represented by this Parameter object.
int	hashCode()	Returns a hash code based on the executable's hash code and the index.
boolean	isImplicit()	Returns true if this parameter is implicitly declared in source code; returns false otherwise.
boolean	isNamePresent()	Returns true if the parameter has a name according to the class file; returns false otherwise.
boolean	isSynthetic()	Returns true if this parameter is neither implicitly nor explicitly declared in source code; returns false otherwise.
boolean	isVarArgs()	Returns true if this parameter represents a variable argument list; returns false otherwise.
String	toString()	Returns a string describing this parameter.

Methods declared in class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods declared in interface java.lang.reflect.AnnotatedElement

isAnnotationPresent

Method Details

equals

public boolean equals(Object obj)

Compares based on the executable and the index.

Overrides:

equals in class Object

Parameters:

obj - The object to compare.

Returns:

Whether or not this is equal to the argument.

See Also:

• Object.hashCode()
• HashMap

hashCode

public int hashCode()

Returns a hash code based on the executable's hash code and the index.

Overrides:

hashCode in class Object

Returns:

A hash code based on the executable's hash code.

See Also:

• Object.equals(java.lang.Object)
• System.identityHashCode(java.lang.Object)

isNamePresent

public boolean isNamePresent()

Returns true if the parameter has a name according to the class file; returns false otherwise. Whether a parameter has a name is determined by the MethodParameters attribute of the method which declares the parameter.

Returns:

true if and only if the parameter has a name according to the class file.

toString

public String toString()

Returns a string describing this parameter. The format is the modifiers for the parameter, if any, in canonical order as recommended by The Java Language Specification, followed by the fully-qualified type of the parameter (excluding the last [] if the parameter is variable arity), followed by "..." if the parameter is variable arity, followed by a space, followed by the name of the parameter.

Overrides:

toString in class Object

Returns:

A string representation of the parameter and associated information.

getDeclaringExecutable

public Executable getDeclaringExecutable()

Returns the Executable declaring this parameter.

Returns:

the Executable declaring this parameter

getModifiers

public int getModifiers()

Returns the Java language modifiers for the parameter represented by this object.

Returns:

the Java language modifiers for the parameter represented by this object

See Java Language Specification:

8.4.1 Formal Parameters

See Also:

• Java programming language and JVM modeling in core reflection

accessFlags

public Set<AccessFlag> accessFlags()

Returns an unmodifiable set of the access flags for the parameter represented by this object, possibly empty.

Returns:

an unmodifiable set of the access flags for the parameter represented by this object, possibly empty

See Java Virtual Machine Specification:

4.7.24 The MethodParameters Attribute

Since:

20

See Also:

• getModifiers()

getName

public String getName()

Returns the name of the parameter. If the parameter's name is present, then this method returns the name provided by the class file. Otherwise, this method synthesizes a name of the form argN, where N is the index of the parameter in the descriptor of the method which declares the parameter.

Returns:

The name of the parameter, either provided by the class file or synthesized if the class file does not provide a name.

getParameterizedType

public Type getParameterizedType()

Returns a Type object that identifies the parameterized type for the parameter represented by this Parameter object.

Returns:

a Type object identifying the parameterized type of the parameter represented by this object

getType

public Class<?> getType()

Returns a Class object that identifies the declared type for the parameter represented by this Parameter object.

Returns:

a Class object identifying the declared type of the parameter represented by this object

getAnnotatedType

public AnnotatedType getAnnotatedType()

Returns an AnnotatedType object that represents the use of a type to specify the type of the formal parameter represented by this Parameter.

Returns:

an AnnotatedType object representing the use of a type to specify the type of the formal parameter represented by this Parameter

isImplicit

public boolean isImplicit()

Returns true if this parameter is implicitly declared in source code; returns false otherwise.

Returns:

true if and only if this parameter is implicitly declared as defined by The Java Language Specification.

isSynthetic

public boolean isSynthetic()

Returns true if this parameter is neither implicitly nor explicitly declared in source code; returns false otherwise.

Returns:

true if and only if this parameter is a synthetic construct as defined by The Java Language Specification.

See Java Language Specification:

13.1 The Form of a Binary

See Also:

• Java programming language and JVM modeling in core reflection

isVarArgs

public boolean isVarArgs()

Returns true if this parameter represents a variable argument list; returns false otherwise.

Returns:

true if an only if this parameter represents a variable argument list.

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.

Note that any annotation returned by this method is a declaration annotation.

Specified by:

getAnnotation in interface AnnotatedElement

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

getAnnotationsByType

public <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass)

Returns annotations that are associated with this element. If there are no annotations associated with this element, the return value is an array of length 0. The difference between this method and AnnotatedElement.getAnnotation(Class) is that this method detects if its argument is a repeatable annotation type (JLS 9.6), and if so, attempts to find one or more annotations of that type by "looking through" a container annotation. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.

Note that any annotations returned by this method are declaration annotations.

Specified by:

getAnnotationsByType in interface AnnotatedElement

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:

all this element's annotations for the specified annotation type if associated with this element, else an array of length zero

Throws:

NullPointerException - if the given annotation class is null

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.

Note that any annotations returned by this method are declaration annotations.

Specified by:

getDeclaredAnnotations in interface AnnotatedElement

Returns:

annotations directly present on this element

getDeclaredAnnotation

public <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass)

Returns this element's annotation for the specified type if such an annotation is directly present, else null. This method ignores inherited annotations. (Returns null if no annotations are directly present on this element.)

Note that any annotation returned by this method is a declaration annotation.

Specified by:

getDeclaredAnnotation in interface AnnotatedElement

Type Parameters:

T - the type of the annotation to query for and return if directly present

Parameters:

annotationClass - the Class object corresponding to the annotation type

Returns:

this element's annotation for the specified annotation type if directly present on this element, else null

Throws:

NullPointerException - if the given annotation class is null

getDeclaredAnnotationsByType

public <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass)

Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present. This method ignores inherited annotations. If there are no specified annotations directly or indirectly present on this element, the return value is an array of length 0. The difference between this method and AnnotatedElement.getDeclaredAnnotation(Class) is that this method detects if its argument is a repeatable annotation type (JLS 9.6), and if so, attempts to find one or more annotations of that type by "looking through" a container annotation if one is present. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.

Note that any annotations returned by this method are declaration annotations.

Specified by:

getDeclaredAnnotationsByType in interface AnnotatedElement

Type Parameters:

T - the type of the annotation to query for and return if directly or indirectly present

Parameters:

annotationClass - the Class object corresponding to the annotation type

Returns:

all this element's annotations for the specified annotation type if directly or indirectly present on this element, else an array of length zero

Throws:

NullPointerException - if the given annotation class is null

getAnnotations

public Annotation[] getAnnotations()

Returns annotations that are present on this element. If there are no annotations 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.

Note that any annotations returned by this method are declaration annotations.

Specified by:

getAnnotations in interface AnnotatedElement

Returns:

annotations present on this element