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Constructor.javaAPI DocJava SE 6 API25774Tue Jun 10 00:25:40 BST 2008java.lang.reflect

Constructor

public final class Constructor 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.

param
the class in which the constructor is declared
see
Member
see
java.lang.Class
see
java.lang.Class#getConstructors()
see
java.lang.Class#getConstructor(Class[])
see
java.lang.Class#getDeclaredConstructors()
author
Kenneth Russell
author
Nakul Saraiya

Fields Summary
private Class
clazz
private int
slot
private Class[]
parameterTypes
private Class[]
exceptionTypes
private int
modifiers
private transient String
signature
private transient ConstructorRepository
genericInfo
private byte[]
annotations
private byte[]
parameterAnnotations
private volatile Class
securityCheckCache
private static final int
LANGUAGE_MODIFIERS
private volatile ConstructorAccessor
constructorAccessor
private Constructor
root
private static final Annotation[]
EMPTY_ANNOTATION_ARRAY
private transient Map
declaredAnnotations
Constructors Summary
Constructor(Class declaringClass, Class[] parameterTypes, Class[] checkedExceptions, int modifiers, int slot, String signature, byte[] annotations, byte[] parameterAnnotations)
Package-private constructor used by ReflectAccess to enable instantiation of these objects in Java code from the java.lang package via sun.reflect.LangReflectAccess.

        this.clazz = declaringClass;
        this.parameterTypes = parameterTypes;
        this.exceptionTypes = checkedExceptions;
        this.modifiers = modifiers;
        this.slot = slot;
        this.signature = signature;
        this.annotations = annotations;
        this.parameterAnnotations = parameterAnnotations;
    
Methods Summary
private voidacquireConstructorAccessor()

        // First check to see if one has been created yet, and take it
        // if so.
        ConstructorAccessor tmp = null;
        if (root != null) tmp = root.getConstructorAccessor();
        if (tmp != null) {
            constructorAccessor = tmp;
            return;
        }
        // Otherwise fabricate one and propagate it up to the root
        tmp = reflectionFactory.newConstructorAccessor(this);
        setConstructorAccessor(tmp);
    
java.lang.reflect.Constructorcopy()
Package-private routine (exposed to java.lang.Class via ReflectAccess) which returns a copy of this Constructor. The copy's "root" field points to this Constructor.

        // This routine enables sharing of ConstructorAccessor objects
        // among Constructor objects which refer to the same underlying
        // method in the VM. (All of this contortion is only necessary
        // because of the "accessibility" bit in AccessibleObject,
        // which implicitly requires that new java.lang.reflect
        // objects be fabricated for each reflective call on Class
        // objects.)
        Constructor<T> res = new Constructor<T>(clazz,
						parameterTypes,
						exceptionTypes, modifiers, slot,
                                                signature,
                                                annotations,
                                                parameterAnnotations);
        res.root = this;
        // Might as well eagerly propagate this if already present
        res.constructorAccessor = constructorAccessor;
        return res;
    
private synchronized java.util.MapdeclaredAnnotations()

        if (declaredAnnotations == null) {
            declaredAnnotations = AnnotationParser.parseAnnotations(
                annotations, sun.misc.SharedSecrets.getJavaLangAccess().
                getConstantPool(getDeclaringClass()),
                getDeclaringClass());
        }
        return declaredAnnotations;
    
public booleanequals(java.lang.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.

	if (obj != null && obj instanceof Constructor) {
	    Constructor other = (Constructor)obj;
	    if (getDeclaringClass() == other.getDeclaringClass()) {
		/* Avoid unnecessary cloning */
		Class[] params1 = parameterTypes;
		Class[] params2 = other.parameterTypes;
		if (params1.length == params2.length) {
		    for (int i = 0; i < params1.length; i++) {
			if (params1[i] != params2[i])
			    return false;
		    }
		    return true;
		}
	    }
	}
	return false;
    
public TgetAnnotation(java.lang.Class annotationClass)

throws
NullPointerException {@inheritDoc}
since
1.5

        if (annotationClass == null)
            throw new NullPointerException();

        return (T) declaredAnnotations().get(annotationClass);
    
sun.reflect.ConstructorAccessorgetConstructorAccessor()

        return constructorAccessor;
    
public java.lang.annotation.Annotation[]getDeclaredAnnotations()

since
1.5


           
        
        return declaredAnnotations().values().toArray(EMPTY_ANNOTATION_ARRAY);
    
public java.lang.ClassgetDeclaringClass()
Returns the Class object representing the class that declares the constructor represented by this Constructor object.

	return clazz;
    
public java.lang.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.

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

	return (Class<?>[])exceptionTypes.clone();
    
private sun.reflect.generics.factory.GenericsFactorygetFactory()


    // Generics infrastructure
    // Accessor for factory
       
	// create scope and factory
	return CoreReflectionFactory.make(this, ConstructorScope.make(this)); 
    
public java.lang.reflect.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 parameterized type, the Type object returned for it must accurately reflect the actual type parameters used in the source code.

If an exception type is a type variable or a parameterized type, it is created. Otherwise, it is resolved.

return
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, 3rd edition
throws
TypeNotPresentException if the underlying method's throws clause refers to a non-existent type declaration
throws
MalformedParameterizedTypeException if the underlying method's throws clause refers to a parameterized type that cannot be instantiated for any reason
since
1.5

	  Type[] result;
	  if (getSignature() != null && 
	      ( (result = getGenericInfo().getExceptionTypes()).length > 0  ))
	      return result;
	  else
	      return getExceptionTypes();
      
private sun.reflect.generics.repository.ConstructorRepositorygetGenericInfo()

	// lazily initialize repository if necessary
	if (genericInfo == null) {
	    // create and cache generic info repository
	    genericInfo = 
		ConstructorRepository.make(getSignature(), 
					   getFactory());
	}
	return genericInfo; //return cached repository
    
public java.lang.reflect.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.

return
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, 3rd edition
throws
TypeNotPresentException if any of the parameter types of the underlying method refers to a non-existent type declaration
throws
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

	if (getSignature() != null)
	    return getGenericInfo().getParameterTypes();
	else
	    return getParameterTypes();
    
public intgetModifiers()
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.

see
Modifier

	return modifiers;
    
public java.lang.StringgetName()
Returns the name of this constructor, as a string. This is always the same as the simple name of the constructor's declaring class.

	return getDeclaringClass().getName();
    
public java.lang.annotation.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.

return
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

        int numParameters = parameterTypes.length;
        if (parameterAnnotations == null)
            return new Annotation[numParameters][0];

        Annotation[][] result = AnnotationParser.parseParameterAnnotations(
            parameterAnnotations,
            sun.misc.SharedSecrets.getJavaLangAccess().
                getConstantPool(getDeclaringClass()),
            getDeclaringClass());
        if (result.length != numParameters) {
	    Class<?> declaringClass = getDeclaringClass();
	    if (declaringClass.isEnum() || 
		declaringClass.isAnonymousClass() || 
		declaringClass.isLocalClass() )
		; // Can't do reliable parameter counting
	    else { 
		if (!declaringClass.isMemberClass() || // top-level 
		    // Check for the enclosing instance parameter for
		    // non-static member classes
		    (declaringClass.isMemberClass() && 
		     ((declaringClass.getModifiers() & Modifier.STATIC) == 0)  && 
		     result.length + 1 != numParameters) ) {
		    throw new AnnotationFormatError(
			      "Parameter annotations don't match number of parameters");
		}
	    }
	}
        return result;
    
public java.lang.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.

return
the parameter types for the constructor this object represents

	return (Class<?>[]) parameterTypes.clone();
    
byte[]getRawAnnotations()

        return annotations;
    
byte[]getRawParameterAnnotations()

        return parameterAnnotations;
    
java.lang.StringgetSignature()

	    return signature;
   
intgetSlot()

        return slot;
    
public java.lang.reflect.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. Returns an array of length 0 if the underlying generic declaration declares no type variables.

return
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, 3rd edition
since
1.5

      if (getSignature() != null) {
	return (TypeVariable<Constructor<T>>[])getGenericInfo().getTypeParameters();
      } else
          return (TypeVariable<Constructor<T>>[])new TypeVariable[0];
    
public inthashCode()
Returns a hashcode for this Constructor. The hashcode is the same as the hashcode for the underlying constructor's declaring class name.

	return getDeclaringClass().getName().hashCode();
    
public booleanisSynthetic()
Returns true if this constructor is a synthetic constructor; returns false otherwise.

return
true if and only if this constructor is a synthetic constructor as defined by the Java Language Specification.
since
1.5

        return Modifier.isSynthetic(getModifiers());
    
public booleanisVarArgs()
Returns true if this constructor was declared to take a variable number of arguments; returns false otherwise.

return
true if an only if this constructor was declared to take a variable number of arguments.
since
1.5

        return (getModifiers() & Modifier.VARARGS) != 0;
    
public TnewInstance(java.lang.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 The Java Language Specification, section 15.9.3.

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.

param
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 {@link java.lang.Float Float})
return
a new object created by calling the constructor this object represents
exception
IllegalAccessException if this Constructor object enforces Java language access control and the underlying constructor is inaccessible.
exception
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.
exception
InstantiationException if the class that declares the underlying constructor represents an abstract class.
exception
InvocationTargetException if the underlying constructor throws an exception.
exception
ExceptionInInitializerError if the initialization provoked by this method fails.

        if (!override) {
            if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
                Class caller = Reflection.getCallerClass(2);
                if (securityCheckCache != caller) {
                    Reflection.ensureMemberAccess(caller, clazz, null, modifiers);
                    securityCheckCache = caller;
                }
            }
        }
	if ((clazz.getModifiers() & Modifier.ENUM) != 0) 
	    throw new IllegalArgumentException("Cannot reflectively create enum objects");
        if (constructorAccessor == null) acquireConstructorAccessor();
        return (T) constructorAccessor.newInstance(initargs);
    
voidsetConstructorAccessor(sun.reflect.ConstructorAccessor accessor)

        constructorAccessor = accessor;
        // Propagate up
        if (root != null) {
            root.setConstructorAccessor(accessor);
        }
    
public java.lang.StringtoGenericString()
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. 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.

return
a string describing this Constructor, include type parameters
since
1.5

	try {
	    StringBuilder sb = new StringBuilder();
	    int mod = getModifiers() & LANGUAGE_MODIFIERS;
	    if (mod != 0) {
		sb.append(Modifier.toString(mod) + " ");
	    }
	    Type[] typeparms = getTypeParameters();
	    if (typeparms.length > 0) {
		boolean first = true;
		sb.append("<");
		for(Type typeparm: typeparms) {
		    if (!first)
			sb.append(",");
		    if (typeparm instanceof Class)
			sb.append(((Class)typeparm).getName());
		    else
			sb.append(typeparm.toString());
		    first = false;
		}
		sb.append("> ");
	    }
	    sb.append(Field.getTypeName(getDeclaringClass()));
	    sb.append("(");
	    Type[] params = getGenericParameterTypes();
	    for (int j = 0; j < params.length; j++) {
		sb.append((params[j] instanceof Class)?
			  Field.getTypeName((Class)params[j]):
			  (params[j].toString()) );
		if (j < (params.length - 1))
		    sb.append(",");
	    }
	    sb.append(")");
	    Type[] exceptions = getGenericExceptionTypes();
	    if (exceptions.length > 0) {
		sb.append(" throws ");
		for (int k = 0; k < exceptions.length; k++) {
		    sb.append((exceptions[k] instanceof Class)?
			      ((Class)exceptions[k]).getName():
			      exceptions[k].toString());
		    if (k < (exceptions.length - 1))
			sb.append(",");
		}
	    }
	    return sb.toString();
	} catch (Exception e) {
	    return "<" + e + ">";
	}
    
public java.lang.StringtoString()
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.

	try {
	    StringBuffer sb = new StringBuffer();
	    int mod = getModifiers() & LANGUAGE_MODIFIERS;
	    if (mod != 0) {
		sb.append(Modifier.toString(mod) + " ");
	    }
	    sb.append(Field.getTypeName(getDeclaringClass()));
	    sb.append("(");
	    Class[] params = parameterTypes; // avoid clone
	    for (int j = 0; j < params.length; j++) {
		sb.append(Field.getTypeName(params[j]));
		if (j < (params.length - 1))
		    sb.append(",");
	    }
	    sb.append(")");
	    Class[] exceptions = exceptionTypes; // avoid clone
	    if (exceptions.length > 0) {
		sb.append(" throws ");
		for (int k = 0; k < exceptions.length; k++) {
		    sb.append(exceptions[k].getName());
		    if (k < (exceptions.length - 1))
			sb.append(",");
		}
	    }
	    return sb.toString();
	} catch (Exception e) {
	    return "<" + e + ">";
	}