org.codehaus.groovy.runtime

## Class NullObject

- java.lang.Object
- - groovy.lang.GroovyObjectSupport
  - - org.codehaus.groovy.runtime.NullObject

- All Implemented Interfaces:
    GroovyObject

      public class NullObject
      extends GroovyObjectSupport

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `asBoolean()` A null object always coerces to false.
    `java.lang.Object` | `asType(java.lang.Class c)` Type conversion method for null.
    `java.lang.Object` | `clone()` Since this is implemented as a singleton, we should avoid the use of the clone method
    `boolean` | `equals(java.lang.Object to)` null is only equal to null
    `static NullObject` | `getNullObject()` get the NullObject reference
    `java.lang.Object` | `getProperty(java.lang.String property)` Tries to get a property on null, which will always fail
    `int` | `hashCode()`
    `java.lang.Object` | `invokeMethod(java.lang.String name, java.lang.Object args)` Tries to invoke a method on null, which will always fail
    `boolean` | `is(java.lang.Object other)` The method "is" is used to test for equal references.
    `java.util.Iterator` | `iterator()` iterator() method to be able to iterate on null.
    `java.lang.Object` | `plus(java.lang.Object o)` Fallback for null+null.
    `java.lang.Object` | `plus(java.lang.String s)` Allows to add a String to null.
    `void` | `setProperty(java.lang.String property, java.lang.Object newValue)` Tries to set a property on null, which will always fail
    `java.lang.String` | `toString()`

    - ### Methods inherited from class groovy.lang.GroovyObjectSupport

      `getMetaClass, setMetaClass`

    - ### Methods inherited from class java.lang.Object

      `finalize, getClass, notify, notifyAll, wait, wait, wait`

- - ### Method Detail

    - #### getNullObject

          public static NullObject getNullObject()

      get the NullObject reference
      Returns:
        the null object

    - #### clone

          public java.lang.Object clone()

      Since this is implemented as a singleton, we should avoid the use of the clone method
      Overrides:
        `clone` in class `java.lang.Object`

    - #### getProperty

          public java.lang.Object getProperty(java.lang.String property)

      Tries to get a property on null, which will always fail
      Specified by:
        `getProperty` in interface `GroovyObject`
      Overrides:
        `getProperty` in class `GroovyObjectSupport`
      Parameters:
        `property` - - the property to get
      Returns:
        a NPE

    - #### setProperty

          public void setProperty(java.lang.String property,
                         java.lang.Object newValue)

      Tries to set a property on null, which will always fail
      Specified by:
        `setProperty` in interface `GroovyObject`
      Overrides:
        `setProperty` in class `GroovyObjectSupport`
      Parameters:
        `property` - - the proprty to set
        `newValue` - - the new value of the property

    - #### invokeMethod

          public java.lang.Object invokeMethod(java.lang.String name,
                                      java.lang.Object args)

      Tries to invoke a method on null, which will always fail
      Specified by:
        `invokeMethod` in interface `GroovyObject`
      Overrides:
        `invokeMethod` in class `GroovyObjectSupport`
      Parameters:
        `name` - the name of the method to invoke
        `args` - - arguments to the method
      Returns:
        a NPE

    - #### equals

          public boolean equals(java.lang.Object to)

      null is only equal to null
      Overrides:
        `equals` in class `java.lang.Object`
      Parameters:
        `to` - - the reference object with which to compare
      Returns:
        - true if this object is the same as the to argument

    - #### iterator

          public java.util.Iterator iterator()

      iterator() method to be able to iterate on null. Note: this part is from Invoker
      Returns:
        an iterator for an empty list

    - #### plus

          public java.lang.Object plus(java.lang.String s)

      Allows to add a String to null. The result is concatenated String of the result of calling toString() on this object and the String in the parameter.
      Parameters:
        `s` - - the String to concatenate
      Returns:
        the concatenated string

    - #### plus

          public java.lang.Object plus(java.lang.Object o)

      Fallback for null+null. The result is always a NPE. The plus(String) version will catch the case of adding a non null String to null.
      Parameters:
        `o` - - the Object
      Returns:
        nothing

    - #### is

          public boolean is(java.lang.Object other)

      The method "is" is used to test for equal references. This method will return true only if the given parameter is null
      Parameters:
        `other` - - the object to test
      Returns:
        true if other is null

    - #### asType

          public java.lang.Object asType(java.lang.Class c)

      Type conversion method for null.
      Parameters:
        `c` - - the class to convert to
      Returns:
        always null

    - #### asBoolean

          public boolean asBoolean()

      A null object always coerces to false.
      Returns:
        false

    - #### toString

          public java.lang.String toString()

      Overrides:
        `toString` in class `java.lang.Object`

    - #### hashCode

          public int hashCode()

      Overrides:
        `hashCode` in class `java.lang.Object`