JavaTM 2 Platform
Std. Ed. v1.3.1

java.lang.reflect
Class Constructor

java.lang.Object
  |
  +--java.lang.reflect.AccessibleObject
        |
        +--java.lang.reflect.Constructor
All Implemented Interfaces:
Member

public final class Constructor
extends AccessibleObject
implements 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()

Fields inherited from interface java.lang.reflect.Member
DECLARED, PUBLIC
 
Method Summary
 boolean equals(Object obj)
          Compares this Constructor against the specified object.
 Class 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 of exceptions declared to be thrown by the underlying constructor 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.
 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.
 int hashCode()
          Returns a hashcode for this Constructor.
 Object 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 toString()
          Returns a string describing this Constructor.
 
Methods inherited from class java.lang.reflect.AccessibleObject
isAccessible, setAccessible, setAccessible
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Method Detail

getDeclaringClass

public Class getDeclaringClass()
Returns the Class object representing the class that declares the constructor represented by this Constructor object.
Specified by:
getDeclaringClass in interface Member

getName

public String getName()
Returns the name of this constructor, as a string. This is always the same as the simple name of the constructor's declaring class.
Specified by:
getName in interface 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
See Also:
Modifier

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.

getExceptionTypes

public Class[] getExceptionTypes()
Returns an array of Class objects that represent the types of 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.

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
Following copied from class: java.lang.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:
Boolean.hashCode(), Hashtable

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
Following copied from class: java.lang.Object
Returns:
a hash code value for this object.
See Also:
Object.equals(java.lang.Object), Hashtable

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
Following copied from class: java.lang.Object
Returns:
a string representation of the object.

newInstance

public Object 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. Returns the newly created and initialized object.

Creation proceeds with the following steps, in order:

If the class that declares the underlying constructor represents an abstract class, the creation throws an InstantiationException.

If this Constructor object enforces Java language access control and the underlying constructor is inaccessible, the creation throws an IllegalAccessException.

If the number of actual parameters supplied via initargs is different from the number of formal parameters required by the underlying constructor, the creation throws an IllegalArgumentException.

A new instance of the constructor's declaring class is created, and its fields are initialized to their default initial values.

For each actual parameter in the supplied initargs array:

If the corresponding formal parameter has a primitive type, an unwrapping conversion is attempted to convert the object value to a value of the primitive type. If this attempt fails, the creation throws an IllegalArgumentException.

If, after possible unwrapping, the parameter value cannot be converted to the corresponding formal parameter type by a method invocation conversion, the creation throws an IllegalArgumentException.

The constructor's declaring class is initialized if it has not already been initialized. A new instance of the constructor's declaring class is created, and its fields are initialized to their default initial values.

Control transfers to the underlying constructor to initialize the new instance. If the constructor completes abruptly by throwing an exception, the exception is placed in an InvocationTargetException and thrown in turn to the caller of newInstance.

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

Throws:
IllegalAccessException - if the underlying constructor is inaccessible.
IllegalArgumentException - if the number of actual and formal parameters differ, or if an unwrapping or method invocation conversion fails.
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.

JavaTM 2 Platform
Std. Ed. v1.3.1

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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

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