Class NullPointerException

java.lang.Object
java.lang.Throwable
java.lang.Exception
java.lang.RuntimeException
java.lang.NullPointerException
All Implemented Interfaces:
Serializable
public classNullPointerExceptionextendsRuntimeException
Thrown when an application attempts to usenull in a case where an object is required. These include:
  • Calling the instance method of anull object.
  • Accessing or modifying the field of anull object.
  • Taking the length ofnull as if it were an array.
  • Accessing or modifying the slots ofnull as if it were an array.
  • Throwingnull as if it were aThrowable value.

Applications should throw instances of this class to indicate other illegal uses of thenull object.NullPointerException objects may be constructed by the virtual machine as ifsuppression were disabled and/or the stack trace was not writable.

Since:
1.0
See Also:

  • Constructor Details

    • NullPointerException

      public NullPointerException()
      Constructs aNullPointerException with no detail message.

    • NullPointerException

      public NullPointerException(String s)
      Constructs aNullPointerException with the specified detail message.
      Parameters:
      s - the detail message.

  • Method Details

    • getMessage

      public String getMessage()
      Returns the detail message string of this throwable.

      If a non-null message was supplied in a constructor it is returned. Otherwise, an implementation specific message ornull is returned.

      Overrides:
      getMessage in class Throwable
      Implementation Note:
      If no explicit message was passed to the constructor, and as long as certain internal information is available, a verbose description of the null reference is returned. The internal information is not available in deserialized NullPointerExceptions.
      Returns:
      the detail message string, which may benull.