Package java.lang.reflect

Class Constructor<T>

java.lang.Object
java.lang.reflect.AccessibleObject
java.lang.reflect.Constructor<T>
Type Parameters:
T - the class that declares this constructor
All Implemented Interfaces:
AnnotatedElement, GenericDeclaration, Member
public final class Constructor<T>
extends AccessibleObject
implements GenericDeclaration, Member
This class represents a constructor. Information about the constructor can be accessed, and the constructor can be invoked dynamically.

  • Method Details

    • getSignatureAttribute

      protected String getSignatureAttribute()

    • getTypeParameters

      public TypeVariable<Constructor<T>>[] getTypeParameters()
      Description copied from interface: GenericDeclaration
      Returns the declared type parameters in declaration order. If there are no type parameters, this method returns a zero length array.
      Specified by:
      getTypeParameters in interface GenericDeclaration
      Returns:
      the declared type parameters in declaration order

    • toGenericString

      public String toGenericString()
      Returns the string representation of the constructor's declaration, including the type parameters.
      Returns:
      the string representation of the constructor's declaration

    • getGenericParameterTypes

      public Type[] getGenericParameterTypes()
      Returns the generic parameter types as an array of Type instances, in declaration order. If this constructor has no generic parameters, an empty array is returned.
      Returns:
      the parameter types
      Throws:
      GenericSignatureFormatError - if the generic constructor signature is invalid
      TypeNotPresentException - if any parameter type points to a missing type
      MalformedParameterizedTypeException - if any parameter type points to a type that cannot be instantiated for some reason

    • getGenericExceptionTypes

      public Type[] getGenericExceptionTypes()
      Returns the exception types as an array of Type instances. If this constructor has no declared exceptions, an empty array will be returned.
      Returns:
      an array of generic exception types
      Throws:
      GenericSignatureFormatError - if the generic constructor signature is invalid
      TypeNotPresentException - if any exception type points to a missing type
      MalformedParameterizedTypeException - if any exception type points to a type that cannot be instantiated for some reason

    • getDeclaredAnnotations

      protected Annotation[] getDeclaredAnnotations​(boolean copy)
      Overrides:
      getDeclaredAnnotations in class AccessibleObject

    • getParameterAnnotations

      public Annotation[][] getParameterAnnotations()
      Returns an array of arrays that represent the annotations of the formal parameters of this constructor. If there are no parameters on this constructor, then an empty array is returned. If there are no annotations set, then an array of empty arrays is returned.
      Returns:
      an array of arrays of Annotation instances

    • isVarArgs

      public boolean isVarArgs()
      Indicates whether or not this constructor takes a variable number of arguments.
      Returns:
      true if a vararg is declare, otherwise false

    • isSynthetic

      public boolean isSynthetic()
      Indicates whether or not this constructor is synthetic (artificially introduced by the compiler).
      Specified by:
      isSynthetic in interface Member
      Returns:
      true if this constructor is synthetic, false otherwise

    • equals

      public boolean equals​(Object object)
      Indicates whether or not the specified object is equal to this constructor. To be equal, the specified object must be an instance of Constructor with the same declaring class and parameter types as this constructor.
      Overrides:
      equals in class Object
      Parameters:
      object - the object to compare
      Returns:
      true if the specified object is equal to this constructor, false otherwise
      See Also:
      hashCode()

    • getDeclaringClass

      public Class<T> getDeclaringClass()
      Returns the class that declares this constructor.
      Specified by:
      getDeclaringClass in interface Member
      Returns:
      the declaring class

    • getExceptionTypes

      public Class<?>[] getExceptionTypes()
      Returns the exception types as an array of Class instances. If this constructor has no declared exceptions, an empty array will be returned.
      Returns:
      the declared exception classes

    • getModifiers

      public int getModifiers()
      Returns the modifiers for this constructor. The Modifier class should be used to decode the result.
      Specified by:
      getModifiers in interface Member
      Returns:
      the modifiers for this constructor
      See Also:
      Modifier

    • getName

      public String getName()
      Returns the name of this constructor.
      Specified by:
      getName in interface Member
      Returns:
      the name of this constructor

    • getParameterTypes

      public Class<?>[] getParameterTypes()
      Returns an array of the Class objects associated with the parameter types of this constructor. If the constructor was declared with no parameters, an empty array will be returned.
      Returns:
      the parameter types

    • hashCode

      public int hashCode()
      Returns an integer hash code for this constructor. Constructors which are equal return the same value for this method. The hash code for a Constructor is the hash code of the name of the declaring class.
      Overrides:
      hashCode in class Object
      Returns:
      the hash code
      See Also:
      equals(java.lang.Object)

    • newInstance

      public T newInstance​(Object... args) throws InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException
      Returns a new instance of the declaring class, initialized by dynamically invoking the constructor represented by this Constructor object. This reproduces the effect of new declaringClass(arg1, arg2, ... , argN) This method performs the following:
      • A new instance of the declaring class is created. If the declaring class cannot be instantiated (i.e. abstract class, an interface, an array type, or a primitive type) then an InstantiationException is thrown.
      • If this Constructor object is enforcing access control (see AccessibleObject) and this constructor is not accessible from the current context, an IllegalAccessException is thrown.
      • If the number of arguments passed and the number of parameters do not match, an IllegalArgumentException is thrown.
      • For each argument passed:
        • If the corresponding parameter type is a primitive type, the argument is unboxed. If the unboxing fails, an IllegalArgumentException is thrown.
        • If the resulting argument cannot be converted to the parameter type via a widening conversion, an IllegalArgumentException is thrown.
      • The constructor represented by this Constructor object is then invoked. If an exception is thrown during the invocation, it is caught and wrapped in an InvocationTargetException. This exception is then thrown. If the invocation completes normally, the newly initialized object is returned.
      Parameters:
      args - the arguments to the constructor
      Returns:
      the new, initialized, object
      Throws:
      InstantiationException - if the class cannot be instantiated
      IllegalAccessException - if this constructor is not accessible
      IllegalArgumentException - if an incorrect number of arguments are passed, or an argument could not be converted by a widening conversion
      InvocationTargetException - if an exception was thrown by the invoked constructor
      See Also:
      AccessibleObject

    • toString

      public String toString()
      Returns a string containing a concise, human-readable description of this constructor. The format of the string is:
      1. modifiers (if any)
      2. declaring class name
      3. '('
      4. parameter types, separated by ',' (if any)
      5. ')'
      6. 'throws' plus exception types, separated by ',' (if any)
      For example: public String(byte[],String) throws UnsupportedEncodingException
      Overrides:
      toString in class Object
      Returns:
      a printable representation for this constructor