T
- the class in which the constructor is declaredAnnotatedElement
, GenericDeclaration
, Member
public final class Constructor<T> extends Executable
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.
Modifier and Type | Method | Description |
---|---|---|
boolean |
equals |
Compares this Constructor against the specified object. |
AnnotatedType |
getAnnotatedReceiverType() |
Returns an AnnotatedType object that represents the use of a type to specify the receiver type of the method/constructor represented by this Executable object. |
AnnotatedType |
getAnnotatedReturnType() |
Returns an AnnotatedType object that represents the use of a type to specify the return type of the method/constructor represented by this Executable. |
<T extends Annotation> |
getAnnotation |
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 |
getDeclaringClass() |
Returns the Class object representing the class that declares the constructor represented by this object. |
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. |
Type[] |
getGenericExceptionTypes() |
Returns an array of Type objects that represent the exceptions declared to be thrown by this executable object. |
Type[] |
getGenericParameterTypes() |
Returns an array of Type objects that represent the formal parameter types, in declaration order, of the executable represented by this object. |
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 Annotation s that represent the annotations on the formal parameters, in declaration order, of the Executable represented by this object. |
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 Class objects that represent the formal parameter types, in declaration order, of the executable represented by this object. |
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. |
int |
hashCode() |
Returns a hashcode for this Constructor . |
boolean |
isSynthetic() |
Returns true if this executable is a synthetic construct; returns false otherwise. |
boolean |
isVarArgs() |
Returns true if this executable was declared to take a variable number of arguments; returns false otherwise. |
T |
newInstance |
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. |
void |
setAccessible |
Set the accessible flag for this reflected object to the indicated boolean value. |
String |
toGenericString() |
Returns a string describing this Constructor , including type parameters. |
String |
toString() |
Returns a string describing this Constructor . |
accessFlags, getAnnotatedExceptionTypes, getAnnotatedParameterTypes, getAnnotationsByType, getParameters
canAccess, getAnnotations, getDeclaredAnnotation, getDeclaredAnnotationsByType, isAccessible, isAnnotationPresent, setAccessible, trySetAccessible
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
getAnnotations, getDeclaredAnnotation, getDeclaredAnnotationsByType, isAnnotationPresent
public void setAccessible(boolean flag)
accessible
flag for this reflected object to the indicated boolean value. A value of true
indicates that the reflected object should suppress checks for Java language access control when it is used. A value of false
indicates 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 C
to enable access to a member
of declaring class
D
if any of the following hold:
C
and D
are in the same module. public
and D
is public
in a package that the module containing D
exports
to at least the module containing C
. protected
static
, D
is public
in a package that the module containing D
exports to at least the module containing C
, and C
is a subclass of D
. D
is in a package that the module containing D
opens
to at least the module containing C
. All packages in unnamed and open modules are open to all modules and so this method always succeeds when D
is 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 member
of declaring class
D
if and only if:
public
and D
is public
in a package that the module containing D
exports
unconditionally. 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:
The accessible
flag when true
suppresses Java language access control checks to only enable read access to these non-modifiable final fields.
If there is a security manager, its checkPermission
method is first called with a ReflectPermission("suppressAccessChecks")
permission.
A SecurityException
is also thrown if this object is a Constructor
object for the class Class
and flag
is true.
setAccessible
in class AccessibleObject
flag
- the new value for the accessible
flagInaccessibleObjectException
- if access cannot be enabledSecurityException
- if the request is denied by the security manager or this is a constructor for java.lang.Class
public Class<T> getDeclaringClass()
Class
object representing the class that declares the constructor represented by this object.getDeclaringClass
in interface Member
getDeclaringClass
in class Executable
public String getName()
getName
in interface Member
getName
in class Executable
public int getModifiers()
getModifiers
in interface Member
getModifiers
in class Executable
public TypeVariable<Constructor<T>>[] getTypeParameters()
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.getTypeParameters
in interface GenericDeclaration
getTypeParameters
in class Executable
TypeVariable
objects that represent the type variables declared by this generic declarationGenericSignatureFormatError
- if the generic signature of this generic declaration does not conform to the format specified in The Java Virtual Machine Specification
public Class<?>[] getParameterTypes()
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. Note that the constructors of some inner classes may have an implicitly declared parameter in addition to explicitly declared ones.getParameterTypes
in class Executable
public int getParameterCount()
getParameterCount
in class Executable
public Type[] getGenericParameterTypes()
Type
objects 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. Also note that as a modeling artifact, the number of returned parameters can differ depending on whether or not generic information is present. If generic information is present, only parameters explicitly present in the source will be returned; 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 Type
object returned for it must accurately reflect the actual type arguments 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.
getGenericParameterTypes
in class Executable
Type
s that represent the formal parameter types of the underlying executable, in declaration orderGenericSignatureFormatError
- if the generic method signature does not conform to the format specified in The Java Virtual Machine Specification
TypeNotPresentException
- 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 reasonpublic Class<?>[] getExceptionTypes()
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.getExceptionTypes
in class Executable
public Type[] getGenericExceptionTypes()
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.
getGenericExceptionTypes
in class Executable
GenericSignatureFormatError
- if the generic method signature does not conform to the format specified in The Java Virtual Machine Specification
TypeNotPresentException
- if the underlying executable's throws
clause refers to a non-existent type declarationMalformedParameterizedTypeException
- if the underlying executable's throws
clause refers to a parameterized type that cannot be instantiated for any reasonpublic boolean equals(Object obj)
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.public int hashCode()
Constructor
. The hashcode is the same as the hashcode for the underlying constructor's declaring class name.public String toString()
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.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
, protected
or private
. Only one of these may appear, or none if the constructor has default (package) access.
toString
in class Object
Constructor
public String toGenericString()
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, 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
, protected
or private
. Only one of these may appear, or none if the constructor has default (package) access.
toGenericString
in class Executable
Constructor
, include type parameterspublic T newInstance(Object... initargs) throws InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException
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.
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
)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 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.public boolean isVarArgs()
true
if this executable was declared to take a variable number of arguments; returns false
otherwise.isVarArgs
in class Executable
true
if this executable was declared to take a variable number of arguments; returns false
otherwisepublic boolean isSynthetic()
true
if this executable is a synthetic construct; returns false
otherwise.isSynthetic
in interface Member
isSynthetic
in class Executable
public <T extends Annotation> T getAnnotation(Class<T> annotationClass)
Note that any annotation returned by this method is a declaration annotation.
getAnnotation
in interface AnnotatedElement
getAnnotation
in class Executable
T
- the type of the annotation to query for and return if presentannotationClass
- the Class object corresponding to the annotation typeNullPointerException
- if the given annotation class is nullpublic Annotation[] getDeclaredAnnotations()
Note that any annotations returned by this method are declaration annotations.
getDeclaredAnnotations
in interface AnnotatedElement
getDeclaredAnnotations
in class AccessibleObject
public Annotation[][] getParameterAnnotations()
Annotation
s 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. Note that any annotations returned by this method are declaration annotations.
getParameterAnnotations
in class Executable
public AnnotatedType getAnnotatedReturnType()
AnnotatedType
object that represents the use of a type to specify the return type of the method/constructor represented by this Executable. If this Executable
object represents a constructor, the
AnnotatedType
object represents the type of the constructed object. If this Executable
object represents a method, the
AnnotatedType
object represents the use of a type to specify the return type of the method.getAnnotatedReturnType
in class Executable
Executable
public AnnotatedType getAnnotatedReceiverType()
AnnotatedType
object that represents the use of a type to specify the receiver type of the method/constructor represented by this Executable
object. The receiver type of a method/constructor is available only if the method/constructor has a receiver parameter (JLS 8.4.1). If this
Executable
object 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 an AnnotatedType
object representing an element with no annotations. If this Executable
object represents a static method or represents a constructor of a top level, static member, local, or anonymous class, then the return value is null.getAnnotatedReceiverType
in class Executable
Executable
or null
if this Executable
can not have a receiver parameter
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/reflect/Constructor.html