Added in API level 1

Summary: Inherited Constants | Methods | Inherited Methods

Constructor

public final class Constructor
extends Executable

java.lang.Object
↳	java.lang.reflect.AccessibleObject
	↳	java.lang.reflect.Executable
		↳	java.lang.reflect.Constructor<T>

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:

Summary

Inherited constants

From interface java.lang.reflect.Member

`int`	`DECLARED` Identifies the set of declared members of a class or interface.
`int`	`PUBLIC` Identifies the set of all public members of a class or interface, including inherited members.

Public methods
`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 annotations that are directly present on this element.
`Class<T>`	`getDeclaringClass()` Returns the `Class` object representing the class or interface that declares the executable represented by this object.
`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.
`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.
`int`	`getModifiers()` Returns the Java language modifiers for the executable represented by this object.
`String`	`getName()` Returns the name of this constructor, as a string.
`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.
`int`	`getParameterCount()` Returns the number of formal parameters (whether explicitly declared or implicitly declared or neither) for the executable represented by this object.
`Class[]<?>`	`getParameterTypes()` Returns an array of `Class` objects that represent the formal parameter types, in declaration order, of the executable represented by this 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 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.
`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`.

Inherited methods

From class


        
          java.lang.reflect.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.
`<T extends Annotation> T[]`	`getAnnotationsByType(Class<T> annotationClass)` Returns annotations that are associated with this element.
`Annotation[]`	`getDeclaredAnnotations()` Returns annotations that are directly present on this element.
`abstract Class<?>`	`getDeclaringClass()` Returns the `Class` object representing the class or interface that declares the executable represented by this object.
`abstract 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.
`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.
`abstract int`	`getModifiers()` Returns the Java language modifiers for the executable represented by this object.
`abstract String`	`getName()` Returns the name of the executable represented by this object.
`abstract 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.
`int`	`getParameterCount()` Returns the number of formal parameters (whether explicitly declared or implicitly declared or neither) for the executable represented by this object.
`abstract Class[]<?>`	`getParameterTypes()` Returns an array of `Class` objects that represent the formal parameter types, in declaration order, of the executable represented by this object.
`Parameter[]`	`getParameters()` Returns an array of `Parameter` objects that represent all the parameters to the underlying executable represented by this object.
`abstract TypeVariable[]<?>`	`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.
`final boolean`	`isAnnotationPresent(Class<? extends Annotation> annotationType)` Returns true if an annotation for the specified type is present on this element, else false.
`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.
`abstract String`	`toGenericString()` Returns a string describing this `Executable`, including any type parameters.

From class


        
          java.lang.reflect.AccessibleObject

`<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.
`boolean`	`isAccessible()` Get the value of the `accessible` flag for this object.
`boolean`	`isAnnotationPresent(Class<? extends Annotation> annotationClass)` Returns true if an annotation for the specified type is present on this element, else false.
`void`	`setAccessible(boolean flag)` Set the `accessible` flag for this object to the indicated boolean value.
`static void`	`setAccessible(AccessibleObject[] array, boolean flag)` Convenience method to set the `accessible` flag for an array of objects with a single security check (for efficiency).

From class


        
          java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long timeoutMillis, int nanos)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

From interface


        
          java.lang.reflect.GenericDeclaration


        abstract
        
        
        
        
        TypeVariable[]<?>


      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.

From interface


        
          java.lang.reflect.Member

`abstract Class<?>`	`getDeclaringClass()` Returns the Class object representing the class or interface that declares the member or constructor represented by this Member.
`abstract int`	`getModifiers()` Returns the Java language modifiers for the member or constructor represented by this Member, as an integer.
`abstract String`	`getName()` Returns the simple name of the underlying member or constructor represented by this Member.
`abstract boolean`	`isSynthetic()` Returns `true` if this member was introduced by the compiler; returns `false` otherwise.

From interface


        
          java.lang.reflect.AnnotatedElement

`abstract <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.
`abstract Annotation[]`	`getAnnotations()` Returns annotations that are present on this element.
`default <T extends Annotation> T[]`	`getAnnotationsByType(Class<T> annotationClass)` Returns annotations that are associated with this element.
`default <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.
`abstract Annotation[]`	`getDeclaredAnnotations()` Returns annotations that are directly present on this element.
`default <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.
`default boolean`	`isAnnotationPresent(Class<? extends Annotation> annotationClass)` Returns true if an annotation for the specified type is present on this element, else false.

Public methods

equals

Added in API level 1

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.

Parameters
`obj`	`Object`: the reference object with which to compare.

Returns
`boolean`	`true` if this object is the same as the obj argument; `false` otherwise.

getAnnotation

Added in API level 1

public T getAnnotation (Class<T> annotationClass)

Returns this element's annotation for the specified type if such an annotation is present, else null.

Parameters
`annotationClass`	`Class`: the Class object corresponding to the annotation type

Returns
`T`	this element's annotation for the specified annotation type if present on this element, else null

Throws
`NullPointerException`

getDeclaredAnnotations

Added in API level 1

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.

Returns
`Annotation[]`	annotations directly present on this element

getDeclaringClass

Added in API level 1

public Class<T> getDeclaringClass ()

Returns the Class object representing the class or interface that declares the executable represented by this object.

Returns
`Class<T>`	an object representing the declaring class of the underlying member

getExceptionTypes

Added in API level 1

public 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.

Returns
`Class[]<?>`	the exception types declared as being thrown by the executable this object represents

getGenericExceptionTypes

Added in API level 1

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.

Returns
`Type[]`	an array of Types that represent the exception types thrown by the underlying executable

Throws
`GenericSignatureFormatError`
`TypeNotPresentException`
`MalformedParameterizedTypeException`

getGenericParameterTypes

Added in API level 1

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.

Returns
`Type[]`	an array of `Type`s that represent the formal parameter types of the underlying executable, in declaration order

Throws
`GenericSignatureFormatError`
`TypeNotPresentException`
`MalformedParameterizedTypeException`

getModifiers

Added in API level 1

public int getModifiers ()

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

Returns
`int`	the Java language modifiers for the underlying member

getName

Added in API level 1

public String getName ()

Returns the name of this constructor, as a string. This is the binary name of the constructor's declaring class.

Returns
`String`	the simple name of the underlying member

getParameterAnnotations

Added in API level 1

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.

Returns
`Annotation[][]`	an array of arrays that represent the annotations on the formal and implicit parameters, in declaration order, of the executable represented by this object

getParameterCount

Added in API level 26

public int getParameterCount ()

Returns the number of formal parameters (whether explicitly declared or implicitly declared or neither) for the executable represented by this object.

Returns
`int`	The number of formal parameters for the executable this object represents

getParameterTypes

Added in API level 1

public 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.

Returns
`Class[]<?>`	the parameter types for the executable this object represents

getTypeParameters

Added in API level 1

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.

Returns
`TypeVariable[]<Constructor<T>>`	an array of `TypeVariable` objects that represent the type variables declared by this generic declaration

Throws
`GenericSignatureFormatError`

hashCode

Added in API level 1

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.

Returns
`int`	a hash code value for this object.

isSynthetic

Added in API level 1

public boolean isSynthetic ()

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

Returns
`boolean`	true if and only if this executable is a synthetic construct as defined by The Java™ Language Specification.

isVarArgs

Added in API level 1

public boolean isVarArgs ()

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

Returns
`boolean`	`true` if an only if this executable was declared to take a variable number of arguments.

newInstance

Added in API level 1

public 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. 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`	`Object`: 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
`T`	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.

toGenericString

Added in API level 1

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
`String`	a string describing this `Constructor`, include type parameters

toString

Added in API level 1

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.

Returns
`String`	a string describing this `Constructor`