java.lang.reflect

Class Constructor<T>

java.lang.Object

java.lang.reflect.AccessibleObject

java.lang.reflect.Constructor<T>

Type Parameters:

T - the class in which the constructor is declared

All Implemented Interfaces:

AnnotatedElement, GenericDeclaration, Member

public final class Constructor<T>
extends AccessibleObject
implements GenericDeclaration, Member

Constructor provides information about, and access to, a single constructor for a class.

Constructor permits widening conversions to occur when matching the actual parameters to newInstance() with the underlying constructor's formal parameters, but throws an IllegalArgumentException if a narrowing conversion would occur.

See Also:

Member, Class, Class.getConstructors(), Class.getConstructor(Class[]), Class.getDeclaredConstructors()

Field Summary

Fields inherited from interface java.lang.reflect.Member

DECLARED, PUBLIC

Method Summary

Methods

Modifier and Type	Method and Description
boolean	equals(Object obj) Compares this Constructor 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<T>	getDeclaringClass() Returns the Class object representing the class that declares the constructor represented by this Constructor object.
Class<?>[]	getExceptionTypes() Returns an array of Class objects that represent the types of exceptions declared to be thrown by the underlying constructor represented by this Constructor object.
Type[]	getGenericExceptionTypes() Returns an array of Type objects that represent the exceptions declared to be thrown by this Constructor object.
Type[]	getGenericParameterTypes() Returns an array of Type objects that represent the formal parameter types, in declaration order, of the method represented by this Constructor object.
int	getModifiers() Returns the Java language modifiers for the constructor represented by this Constructor object, as an integer.
String	getName() Returns the name of this constructor, 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 Constructor object.
Class<?>[]	getParameterTypes() Returns an array of Class objects that represent the formal parameter types, in declaration order, of the constructor represented by this Constructor object.
TypeVariable<Constructor<T>>[]	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 Constructor.
boolean	isSynthetic() Returns true if this constructor is a synthetic constructor; returns false otherwise.
boolean	isVarArgs() Returns true if this constructor was declared to take a variable number of arguments; returns false otherwise.
T	newInstance(Object... initargs) Uses the constructor represented by this Constructor object to create and initialize a new instance of the constructor's declaring class, with the specified initialization parameters.
String	toGenericString() Returns a string describing this Constructor, including type parameters.
String	toString() Returns a string describing this Constructor.

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<T> getDeclaringClass()

Returns the Class object representing the class that declares the constructor represented by this Constructor 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 this constructor, as a string. This is the binary name of the constructor's declaring class.

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 constructor represented by this Constructor 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<Constructor<T>>[] 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

Since:

1.5

getParameterTypes

public Class<?>[] getParameterTypes()

Returns an array of Class objects that represent the formal parameter types, in declaration order, of the constructor represented by this Constructor object. Returns an array of length 0 if the underlying constructor takes no parameters.

Returns:

the parameter types for the constructor 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 Constructor 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

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 exceptions declared to be thrown by the underlying constructor represented by this Constructor object. Returns an array of length 0 if the constructor declares no exceptions in its throws clause.

Returns:

the exception types declared as being thrown by the constructor this object represents

getGenericExceptionTypes

public Type[] getGenericExceptionTypes()

Returns an array of Type objects that represent the exceptions declared to be thrown by this Constructor object. Returns an array of length 0 if the underlying method 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.

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

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 Constructor against the specified object. Returns true if the objects are the same. Two Constructor objects are the same if they were declared by the same class and have the same formal parameter types.

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 Constructor. The hashcode is the same as the hashcode for the underlying constructor's declaring class 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 Constructor. The string is formatted as the constructor access modifiers, if any, followed by the fully-qualified name of the declaring class, followed by a parenthesized, comma-separated list of the constructor's formal parameter types. For example:

    public java.util.Hashtable(int,float)
 

The only possible modifiers for constructors are the access modifiers public, protected or private. Only one of these may appear, or none if the constructor has default (package) access.

Overrides:

toString in class Object

Returns:

a string representation of the object.

toGenericString

public String toGenericString()

Returns a string describing this Constructor, including type parameters. The string is formatted as the constructor access modifiers, if any, followed by an angle-bracketed comma separated list of the constructor's type parameters, if any, followed by the fully-qualified name of the declaring class, followed by a parenthesized, comma-separated list of the constructor's generic formal parameter types. If this constructor 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 constructor 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 thrown exception types.

The only possible modifiers for constructors are the access modifiers public, protected or private. Only one of these may appear, or none if the constructor has default (package) access.

Returns:

a string describing this Constructor, include type parameters

Since:

1.5

newInstance

public T newInstance(Object... initargs)
              throws InstantiationException,
                     IllegalAccessException,
                     IllegalArgumentException,
                     InvocationTargetException

Uses the constructor represented by this Constructor object to create and initialize a new instance of the constructor's declaring class, with the specified initialization 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 number of formal parameters required by the underlying constructor is 0, the supplied initargs array may be of length 0 or null.

If the constructor's declaring class is an inner class in a non-static context, the first argument to the constructor needs to be the enclosing instance; see section 15.9.3 of The Java™ Language Specification.

If the required access and argument checks succeed and the instantiation will proceed, the constructor's declaring class is initialized if it has not already been initialized.

If the constructor completes normally, returns the newly created and initialized instance.

Parameters:

initargs - array of objects to be passed as arguments to the constructor call; values of primitive types are wrapped in a wrapper object of the appropriate type (e.g. a float in a Float)

Returns:

a new object created by calling the constructor this object represents

Throws:

IllegalAccessException - if this Constructor object is enforcing Java language access control and the underlying constructor is inaccessible.

IllegalArgumentException - 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; if this constructor pertains to an enum type.

InstantiationException - if the class that declares the underlying constructor represents an abstract class.

InvocationTargetException - if the underlying constructor throws an exception.

ExceptionInInitializerError - if the initialization provoked by this method fails.

isVarArgs

public boolean isVarArgs()

Returns true if this constructor was declared to take a variable number of arguments; returns false otherwise.

Returns:

true if an only if this constructor was declared to take a variable number of arguments.

Since:

1.5

isSynthetic

public boolean isSynthetic()

Returns true if this constructor is a synthetic constructor; returns false otherwise.

Specified by:

isSynthetic in interface Member

Returns:

true if and only if this constructor is a synthetic constructor 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

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 Constructor 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 Constructor object

Since:

1.5