Class Undefined

  • All Implemented Interfaces:
    java.io.Serializable

    public class Undefined
    extends java.lang.Object
    implements java.io.Serializable
    This class implements the Undefined value in JavaScript.

    We represent "undefined" internally using two static objects -- "Undefined.instance" and SCRIPTABLE_UNDEFINED. Java code that needs to make something undefined should generally use the first, and use the second if a Scriptable object is absolutely required.

    Java code that needs to test whether something is undefined must use the "isUndefined" method because of the multiple internal representations.

    See Also:
    Serialized Form
    • Field Summary

      Fields 
      Modifier and Type Field Description
      static java.lang.Object instance
      This is the standard value for "undefined" in Rhino.
      static Scriptable SCRIPTABLE_UNDEFINED
      An alternate representation of undefined, to be used only when we need to pass it to a method that takes as Scriptable as a parameter.
    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean equals​(java.lang.Object obj)  
      int hashCode()  
      static boolean isUndefined​(java.lang.Object obj)
      Safely test whether "obj" is undefined.
      java.lang.Object readResolve()  
      • Methods inherited from class java.lang.Object

        clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • instance

        public static final java.lang.Object instance
        This is the standard value for "undefined" in Rhino. Java code that needs to represent "undefined" should use this object (rather than a new instance of this class).
      • SCRIPTABLE_UNDEFINED

        public static final Scriptable SCRIPTABLE_UNDEFINED
        An alternate representation of undefined, to be used only when we need to pass it to a method that takes as Scriptable as a parameter. This is used when we need to pass undefined as the "this" parmeter of a Callable instance, because we cannot change that interface without breaking backward compatibility.
    • Method Detail

      • readResolve

        public java.lang.Object readResolve()
      • equals

        public boolean equals​(java.lang.Object obj)
        Overrides:
        equals in class java.lang.Object
      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class java.lang.Object
      • isUndefined

        public static boolean isUndefined​(java.lang.Object obj)
        Safely test whether "obj" is undefined. Java code must use this function rather than testing the value directly since we have two representations of undefined in Rhino.