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

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

    - ### 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 Object clone()

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

    - #### getProperty

          public Object getProperty(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

    - #### with

          public <T> T with(Closure<T> closure)

      Allows the closure to be called for NullObject
      Parameters:
        `closure` - the closure to call on the object
      Returns:
        result of calling the closure

    - #### setProperty

          public void setProperty(String property,
                                  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 Object invokeMethod(String name,
                                     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(Object to)

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

    - #### iterator

          public 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 Object plus(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 Object plus(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(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 Object asType(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 String toString()

      Overrides:
        `toString` in class `Object`

    - #### hashCode

          public int hashCode()

      Overrides:
        `hashCode` in class `Object`