Skip to content

Most visited

Recently visited

navigation

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

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 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[]<?> 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
From class java.lang.reflect.AccessibleObject
From class java.lang.Object
From interface java.lang.reflect.Member
From interface java.lang.reflect.GenericDeclaration
From interface java.lang.reflect.AnnotatedElement

Public methods

equals

added in API level 1
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
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
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
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
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
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
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 Types that represent the formal parameter types of the underlying executable, in declaration order

Throws
GenericSignatureFormatError
TypeNotPresentException
MalformedParameterizedTypeException

getModifiers

added in API level 1
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
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
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

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
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
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
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
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
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
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
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
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

This site uses cookies to store your preferences for site-specific language and display options.

Get the latest Android developer news and tips that will help you find success on Google Play.

* Required Fields

Hooray!

Browse this site in ?

You requested a page in , but your language preference for this site is .

Would you like to change your language preference and browse this site in ? If you want to change your language preference later, use the language menu at the bottom of each page.

This class requires API level or higher

This doc is hidden because your selected API level for the documentation is . You can change the documentation API level with the selector above the left navigation.

For more information about specifying the API level your app requires, read Supporting Different Platform Versions.

Take a one-minute survey?
Help us improve Android tools and documentation.