Class: 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.

Authors:
@author Kenneth Russell
@author Nakul Saraiya
See:
@see java.lang.reflect.Member
@see Class
@see Class.getConstructors()
@see Class.getConstructor(java.lang.Class[])
@see Class.getDeclaredConstructors()

Inheritance

Superclass tree: Implements:

Methods

  • equalstop

    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:
    @param obj the reference object with which to compare.
    Return:
    @return true if this object is the same as the obj argument; false otherwise.
    Override hierarchy:
    equals from Object
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  • getAnnotationtop

    public <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.
    Return:
    @return this element's annotation for the specified annotation type if present on this element, else null
    Specified by:
    getAnnotation from AnnotatedElement
    Override hierarchy:
    getAnnotation from AccessibleObject
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  • getDeclaredAnnotationstop

    public 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.
    Return:
    @return All annotations directly present on this element
    Specified by:
    getDeclaredAnnotations from AnnotatedElement
    Override hierarchy:
    getDeclaredAnnotations from AccessibleObject
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  • getDeclaringClasstop

    public Class<T> getDeclaringClass()
    Returns the Class object representing the class that declares the constructor represented by this Constructor object.
    Return:
    @return an object representing the declaring class of the underlying member
    Specified by:
    getDeclaringClass from Member
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  • getExceptionTypestop

    public 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:
    @return the exception types declared as being thrown by the constructor this object represents
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  • getGenericExceptionTypestop

    public 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:
    @return an array of Types that represent the exception types thrown by the underlying method
    Exceptions:
    @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:
    @since 1.5
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  • getGenericParameterTypestop

    public 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:
    @return an array of Types that represent the formal parameter types of the underlying method, in declaration order
    Exceptions:
    @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:
    @since 1.5
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  • getModifierstop

    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.
    Return:
    @return the Java language modifiers for the underlying member
    See:
    @see java.lang.reflect.Modifier
    Specified by:
    getModifiers from Member
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  • getNametop

    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.
    Return:
    @return the simple name of the underlying member
    Specified by:
    getName from Member
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  • getParameterAnnotationstop

    public Annotation[][] getParameterAnnotations()
    Returns an array of arrays that represent the annotations on the formal parameters, in declaration order, of the method represented by this Method 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:
    @return an array of arrays that represent the annotations on the formal parameters, in declaration order, of the method represented by this Method object
    Since:
    @since 1.5
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  • getParameterTypestop

    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.
    Return:
    @return the parameter types for the constructor this object represents
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  • getTypeParameterstop

    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.
    Return:
    @return an array of TypeVariable objects that represent the type variables declared by this generic declaration
    Exceptions:
    @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:
    @since 1.5
    Specified by:
    getTypeParameters from GenericDeclaration
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  • hashCodetop

    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.
    Return:
    @return a hash code value for this object.
    Override hierarchy:
    hashCode from Object
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  • isSynthetictop

    public boolean isSynthetic()
    Returns true if this constructor is a synthetic constructor; returns false otherwise.
    Return:
    @return true if and only if this constructor is a synthetic constructor as defined by the Java Language Specification.
    Since:
    @since 1.5
    Specified by:
    isSynthetic from Member
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  • isVarArgstop

    public boolean isVarArgs()
    Returns true if this constructor was declared to take a variable number of arguments; returns false otherwise.
    Return:
    @return true if an only if this constructor was declared to take a variable number of arguments.
    Since:
    @since 1.5
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  • newInstancetop

    public T 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.

    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 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:
    @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 Float )
    Return:
    @return a new object created by calling the constructor this object represents
    Exceptions:
    @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.
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  • toGenericStringtop

    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. 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:
    @return a string describing this Constructor, include type parameters
    Since:
    @since 1.5
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  • toStringtop

    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.

    Return:
    @return a string representation of the object.
    Override hierarchy:
    toString from Object
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