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 |
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Public methods | |
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boolean | equals(Object obj) Compares this |
<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[]<?> | getExceptionTypes() Returns an array of |
Type[] | getGenericExceptionTypes() Returns an array of |
Type[] | getGenericParameterTypes() Returns an array of |
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 |
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 |
TypeVariable[]<Constructor<T>> | getTypeParameters() Returns an array of |
int | hashCode() Returns a hashcode for this |
boolean | isSynthetic() Returns |
boolean | isVarArgs() Returns |
T | newInstance(Object... initargs) Uses the constructor represented by this |
String | toGenericString() Returns a string describing this |
String | toString() Returns a string describing this |
Inherited methods | |
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Public methods
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.
| Parameters | |
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obj | Object: the reference object with which to compare. |
| Returns | |
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boolean | true if this object is the same as the obj argument; false otherwise. |
getAnnotation
public 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 | |
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T | this element's annotation for the specified annotation type if present on this element, else null |
| Throws | |
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NullPointerException | |
getDeclaredAnnotations
public 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
public 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
public 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
public 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 | |
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GenericSignatureFormatError | |
TypeNotPresentException | |
MalformedParameterizedTypeException | |
getGenericParameterTypes
public 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 | |
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GenericSignatureFormatError | |
TypeNotPresentException | |
MalformedParameterizedTypeException | |
getModifiers
public 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
public 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
public 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
public 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
public 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
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.
| Returns | |
|---|---|
TypeVariable[]<Constructor<T>> | an array of TypeVariable objects that represent the type variables declared by this generic declaration |
| Throws | |
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GenericSignatureFormatError | |
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.
| Returns | |
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int | a hash code value for this object. |
isSynthetic
public boolean isSynthetic ()
Returns true if this executable is a synthetic construct; returns false otherwise.
| Returns | |
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boolean | true if and only if this executable is a synthetic construct as defined by The Java™ Language Specification. |
isVarArgs
public 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
public 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
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. 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
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.
| Returns | |
|---|---|
String | a string describing this Constructor |