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Constructor

public final class Constructor
extends AccessibleObject implements GenericDeclaration, Member

java.lang.Object
   ↳ java.lang.reflect.AccessibleObject
     ↳ 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

Fields

protected int accessFlags

Bits encoding access (e.g.

protected Class<?> declaringClass

Method's declaring class

protected Class<?> declaringClassOfOverriddenMethod

Overriden method's declaring class (same as declaringClass unless declaringClass is a proxy class)

protected int dexMethodIndex

The method index of this method within its defining dex file

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.

<A extends Annotation> A getAnnotation(Class<A> annotationType)

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

Annotation[] getAnnotations()

Returns all annotations present on this element.

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 isAnnotationPresent(Class<? extends Annotation> annotationType)
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... args)

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.

Protected methods

int compareParameters(Class[]<?> params)
boolean equalMethodParameters(Class[]<?> params)

Inherited methods

From class java.lang.reflect.AccessibleObject
From class java.lang.Object
From interface java.lang.reflect.AnnotatedElement
From interface java.lang.reflect.GenericDeclaration
From interface java.lang.reflect.Member

Fields

accessFlags

int accessFlags

Bits encoding access (e.g. public, private) as well as other runtime specific flags

declaringClass

Class<?> declaringClass

Method's declaring class

declaringClassOfOverriddenMethod

Class<?> declaringClassOfOverriddenMethod

Overriden method's declaring class (same as declaringClass unless declaringClass is a proxy class)

dexMethodIndex

int dexMethodIndex

The method index of this method within its defining dex file

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

getAnnotation

Added in API level 14
A getAnnotation (Class<A> annotationType)

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

Parameters
annotationType Class: the Class object corresponding to the annotation type
Returns
A this element's annotation for the specified annotation type if present on this element, else null
Throws
NullPointerException

getAnnotations

Added in API level 1
Annotation[] getAnnotations ()

Returns all annotations present on this element. (Returns an array of length zero if this element has no annotations.) 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[] all annotations present on this element

getDeclaredAnnotations

Added in API level 1
Annotation[] getDeclaredAnnotations ()

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.

Returns
Annotation[] All annotations directly present on this element

getDeclaringClass

Added in API level 1
Class<T> getDeclaringClass ()

Returns the Class object representing the class that declares the constructor represented by this Constructor object.

Returns
Class<T>

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

Returns
Class[]<?> the exception types declared as being thrown by the constructor 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 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
Type[] 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

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 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
Type[] 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

getModifiers

Added in API level 1
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.

Returns
int

See also:

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 name of this method

getParameterAnnotations

Added in API level 1
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
Annotation[][] an array of arrays that represent the annotations on the formal parameters, in declaration order, of the method represented by this Constructor object

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 constructor represented by this Constructor object. Returns an array of length 0 if the underlying constructor takes no parameters.

Returns
Class[]<?> the parameter types for the constructor 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 if the generic signature of this generic declaration does not conform to the format specified in The Java™ Virtual Machine Specification

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.

isAnnotationPresent

Added in API level 1
boolean isAnnotationPresent (Class<? extends Annotation> annotationType)

Parameters
annotationType Class
Returns
boolean

isSynthetic

Added in API level 1
boolean isSynthetic ()

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

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

isVarArgs

Added in API level 1
boolean isVarArgs ()

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

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

newInstance

Added in API level 1
T newInstance (Object... args)

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
args 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 representation of the object.

Protected methods

compareParameters

int compareParameters (Class[]<?> params)

Parameters
params Class
Returns
int

equalMethodParameters

boolean equalMethodParameters (Class[]<?> params)

Parameters
params Class
Returns
boolean
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