Class Constructor<T>
- Type Parameters:
T- the class in which the constructor is declared
- All Implemented Interfaces:
AnnotatedElement,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.
- Since:
- 1.1
- See Also:
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Field Summary
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Method Summary
Modifier and TypeMethodDescriptionbooleanCompares thisConstructoragainst the specified object.Returns anAnnotatedTypeobject that represents the use of a type to specify the receiver type of the method/constructor represented by thisExecutableobject.Returns anAnnotatedTypeobject that represents the use of a type to specify the return type of the method/constructor represented by this Executable.<T extends Annotation>
TgetAnnotation(Class<T> annotationClass) Returns this element's annotation for the specified type if such an annotation is present, else null.Returns annotations that are directly present on this element.Returns theClassobject representing the class that declares the constructor represented by this object.Class<?>[]Returns an array ofClassobjects that represent the types of exceptions declared to be thrown by the underlying executable represented by this object.Type[]Returns an array ofTypeobjects that represent the exceptions declared to be thrown by this executable object.Type[]Returns an array ofTypeobjects that represent the formal parameter types, in declaration order, of the executable represented by this object.intReturns the Java language modifiers for the executable represented by this object.getName()Returns the name of this constructor, as a string.Annotation[][]Returns an array of arrays ofAnnotations that represent the annotations on the formal parameters, in declaration order, of theExecutablerepresented by this object.intReturns the number of formal parameters (whether explicitly declared or implicitly declared or neither) for the executable represented by this object.Class<?>[]Returns an array ofClassobjects that represent the formal parameter types, in declaration order, of the executable represented by this object.TypeVariable<Constructor<T>>[]Returns an array ofTypeVariableobjects that represent the type variables declared by the generic declaration represented by thisGenericDeclarationobject, in declaration order.inthashCode()Returns a hashcode for thisConstructor.booleanReturnstrueif this executable is a synthetic construct; returnsfalseotherwise.booleanReturnstrueif this executable was declared to take a variable number of arguments; returnsfalseotherwise.newInstance(Object... initargs) Uses the constructor represented by thisConstructorobject to create and initialize a new instance of the constructor's declaring class, with the specified initialization parameters.voidsetAccessible(boolean flag) Set theaccessibleflag for this reflected object to the indicated boolean value.Returns a string describing thisConstructor, including type parameters.toString()Returns a string describing thisConstructor.Methods declared in class java.lang.reflect.Executable
accessFlags, getAnnotatedExceptionTypes, getAnnotatedParameterTypes, getAnnotationsByType, getParametersMethods declared in class java.lang.reflect.AccessibleObject
canAccess, getAnnotations, getDeclaredAnnotation, getDeclaredAnnotationsByType, isAccessible, isAnnotationPresent, setAccessible, trySetAccessibleMethods declared in class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, waitMethods declared in interface java.lang.reflect.AnnotatedElement
getAnnotations, getDeclaredAnnotation, getDeclaredAnnotationsByType, isAnnotationPresent
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Method Details
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setAccessible
public void setAccessible(boolean flag) Set theaccessibleflag for this reflected object to the indicated boolean value. A value oftrueindicates that the reflected object should suppress checks for Java language access control when it is used. A value offalseindicates that the reflected object should enforce checks for Java language access control when it is used, with the variation noted in the class description.This method may be used by a caller in class
Cto enable access to amemberofdeclaring classDif any of the following hold:-
CandDare in the same module. - The member is
publicandDispublicin a package that the module containingDexportsto at least the module containingC. - The member is
protectedstatic,Dispublicin a package that the module containingDexports to at least the module containingC, andCis a subclass ofD. -
Dis in a package that the module containingDopensto at least the module containingC. All packages in unnamed and open modules are open to all modules and so this method always succeeds whenDis in an unnamed or open module.
This method may be used by JNI code with no caller class on the stack to enable access to a
memberofdeclaring classDif and only if:- The member is
publicandDispublicin a package that the module containingDexportsunconditionally.
This method cannot be used to enable access to private members, members with default (package) access, protected instance members, or protected constructors when the declaring class is in a different module to the caller and the package containing the declaring class is not open to the caller's module.
This method cannot be used to enable write access to a non-modifiable final field. The following fields are non-modifiable:
- static final fields declared in any class or interface
- final fields declared in a hidden class
- final fields declared in a record
The
accessibleflag whentruesuppresses Java language access control checks to only enable read access to these non-modifiable final fields.A
SecurityExceptionis thrown if this object is aConstructorobject for the classClassandflagis true.- Overrides:
setAccessiblein classAccessibleObject- Parameters:
flag- the new value for theaccessibleflag- Throws:
InaccessibleObjectException- if access cannot be enabledSecurityException- if this is a constructor forjava.lang.Class- External Specifications
- See Also:
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getDeclaringClass
Returns theClassobject representing the class that declares the constructor represented by this object.- Specified by:
getDeclaringClassin interfaceMember- Specified by:
getDeclaringClassin classExecutable- Returns:
- an object representing the declaring class of the underlying member
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getName
Returns the name of this constructor, as a string. This is the binary name of the constructor's declaring class.- Specified by:
getNamein interfaceMember- Specified by:
getNamein classExecutable- Returns:
- the simple name of the underlying member
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getModifiers
public int getModifiers()Returns the Java language modifiers for the executable represented by this object.- Specified by:
getModifiersin interfaceMember- Specified by:
getModifiersin classExecutable- Returns:
- the Java language modifiers for the executable represented by this object
- See Java Language Specification:
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8.8.3 Constructor Modifiers
- See Also:
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getTypeParameters
Returns an array ofTypeVariableobjects that represent the type variables declared by the generic declaration represented by thisGenericDeclarationobject, in declaration order. Returns an array of length 0 if the underlying generic declaration declares no type variables.- Specified by:
getTypeParametersin interfaceGenericDeclaration- Specified by:
getTypeParametersin classExecutable- Returns:
- an array of
TypeVariableobjects 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- Since:
- 1.5
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getParameterTypes
Returns an array ofClassobjects 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. Note that the constructors of some inner classes may have an implicitly declared parameter in addition to explicitly declared ones. Also note that compact constructors of a record class may have implicitly declared parameters.- Specified by:
getParameterTypesin classExecutable- Returns:
- the parameter types for the executable this object represents
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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.- Specified by:
getParameterCountin classExecutable- Returns:
- The number of formal parameters for the executable this object represents
- Since:
- 1.8
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getGenericParameterTypes
Returns an array ofTypeobjects that represent the formal parameter types, in declaration order, of the executable represented by this object. An array of length 0 is returned if the underlying executable takes no parameters. Note that the constructors of some inner classes may have an implicitly declared parameter in addition to explicitly declared ones. Compact constructors of a record class may also have implicitly declared parameters, but they are a special case and thus considered as if they had been explicitly declared in the source. Finally note that as amodeling artifact, the number of returned parameters can differ depending on whether or not generic information is present. If generic information is present, parameters explicitly present in the source or parameters of compact constructors of a record class will be returned. Note that parameters of compact constructors of a record class are a special case, as they are not explicitly present in the source, and its type will be returned regardless of the parameters being implicitly declared or not. If generic information is not present, implicit and synthetic parameters may be returned as well.If a formal parameter type is a parameterized type, the
Typeobject returned for it must accurately reflect the actual type arguments used in the source code. This assertion also applies to the parameters of compact constructors of a record class, independently of them being implicitly declared or not.If a formal parameter type is a type variable or a parameterized type, it is created. Otherwise, it is resolved.
- Overrides:
getGenericParameterTypesin classExecutable- Returns:
- an array of
Types that represent the formal parameter types of the underlying executable, in declaration order - Throws:
GenericSignatureFormatError- if the generic method signature does not conform to the format specified in The Java Virtual Machine SpecificationTypeNotPresentException- if any of the parameter types of the underlying executable refers to a non-existent type declarationMalformedParameterizedTypeException- if any of the underlying executable's parameter types refer to a parameterized type that cannot be instantiated for any reason- Since:
- 1.5
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getExceptionTypes
Returns an array ofClassobjects 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 itsthrowsclause.- Specified by:
getExceptionTypesin classExecutable- Returns:
- the exception types declared as being thrown by the executable this object represents
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getGenericExceptionTypes
Returns an array ofTypeobjects 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 itsthrowsclause.If an exception type is a type variable or a parameterized type, it is created. Otherwise, it is resolved.
- Overrides:
getGenericExceptionTypesin classExecutable- Returns:
- an array of Types that represent the exception types thrown by the underlying executable
- Throws:
GenericSignatureFormatError- if the generic method signature does not conform to the format specified in The Java Virtual Machine SpecificationTypeNotPresentException- if the underlying executable'sthrowsclause refers to a non-existent type declarationMalformedParameterizedTypeException- if the underlying executable'sthrowsclause refers to a parameterized type that cannot be instantiated for any reason- Since:
- 1.5
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equals
Compares thisConstructoragainst the specified object. Returns true if the objects are the same. TwoConstructorobjects are the same if they were declared by the same class and have the same formal parameter types. -
hashCode
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toString
Returns a string describing thisConstructor. 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.HashMap(int,float)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,protectedorprivate. Only one of these may appear, or none if the constructor has default (package) access.- Overrides:
toStringin classObject- Returns:
- a string describing this
Constructor - See Java Language Specification:
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8.8.3 Constructor Modifiers
8.9.2 Enum Body Declarations
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toGenericString
Returns a string describing thisConstructor, 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, including informative bounds of the 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 class name. 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 generic thrown exception types.The only possible modifiers for constructors are the access modifiers
public,protectedorprivate. Only one of these may appear, or none if the constructor has default (package) access.- Specified by:
toGenericStringin classExecutable- Returns:
- a string describing this
Constructor, include type parameters - See Java Language Specification:
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8.8.3 Constructor Modifiers
8.9.2 Enum Body Declarations - Since:
- 1.5
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newInstance
public T newInstance(Object... initargs) throws InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException Uses the constructor represented by thisConstructorobject 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
initargsarray 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- 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. afloatin aFloat)- Returns:
- a new object created by calling the constructor this object represents
- Throws:
IllegalAccessException- if thisConstructorobject 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 class.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.
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isVarArgs
public boolean isVarArgs()Returnstrueif this executable was declared to take a variable number of arguments; returnsfalseotherwise.- Overrides:
isVarArgsin classExecutable- Returns:
trueif this executable was declared to take a variable number of arguments; returnsfalseotherwise- See Java Language Specification:
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8.4.1 Formal Parameters
- Since:
- 1.5
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isSynthetic
public boolean isSynthetic()Returnstrueif this executable is a synthetic construct; returnsfalseotherwise.- Specified by:
isSyntheticin interfaceMember- Overrides:
isSyntheticin classExecutable- Returns:
- true if and only if this executable is a synthetic construct as defined by The Java Language Specification.
- See Java Language Specification:
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13.1 The Form of a Binary
- See Java Virtual Machine Specification:
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4.6 Methods
- Since:
- 1.5
- See Also:
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getAnnotation
Returns this element's annotation for the specified type if such an annotation is present, else null.Note that any annotation returned by this method is a declaration annotation.
- Specified by:
getAnnotationin interfaceAnnotatedElement- Overrides:
getAnnotationin classExecutable- Type Parameters:
T- the type of the annotation to query for and return if present- Parameters:
annotationClass- the Class object corresponding to the annotation type- Returns:
- this element's annotation for the specified annotation type if present on this element, else null
- Throws:
NullPointerException- if the given annotation class is null- Since:
- 1.5
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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.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getDeclaredAnnotationsin interfaceAnnotatedElement- Overrides:
getDeclaredAnnotationsin classAccessibleObject- Returns:
- annotations directly present on this element
- Since:
- 1.5
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getParameterAnnotations
Returns an array of arrays ofAnnotations that represent the annotations on the formal parameters, in declaration order, of theExecutablerepresented 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 theExecutablehas 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. SeeParameterfor more information.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getParameterAnnotationsin classExecutable- Returns:
- an array of arrays that represent the annotations on the formal and implicit parameters, in declaration order, of the executable represented by this object
- Since:
- 1.5
- See Also:
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getAnnotatedReturnType
Returns anAnnotatedTypeobject that represents the use of a type to specify the return type of the method/constructor represented by this Executable. If thisExecutableobject represents a constructor, theAnnotatedTypeobject represents the type of the constructed object. If thisExecutableobject represents a method, theAnnotatedTypeobject represents the use of a type to specify the return type of the method.- Specified by:
getAnnotatedReturnTypein classExecutable- Returns:
- an object representing the return type of the method
or constructor represented by this
Executable - Since:
- 1.8
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getAnnotatedReceiverType
Returns anAnnotatedTypeobject that represents the use of a type to specify the receiver type of the method/constructor represented by thisExecutableobject. The receiver type of a method/constructor is available only if the method/constructor has a receiver parameter (JLS 8.4.1). If thisExecutableobject represents an instance method or represents a constructor of an inner member class, and the method/constructor either has no receiver parameter or has a receiver parameter with no annotations on its type, then the return value is anAnnotatedTypeobject representing an element with no annotations. If thisExecutableobject represents a static method or represents a constructor of a top level, static member, local, or anonymous class, then the return value is null.- Overrides:
getAnnotatedReceiverTypein classExecutable- Returns:
- an object representing the receiver type of the method or
constructor represented by this
Executableornullif thisExecutablecan not have a receiver parameter - Since:
- 1.8
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