NullPointerException in java

NullPointerException class is available in java.lang package and it extends RuntimeException class

public class NullPointerException extends RuntimeException

NullPointerException class inherits methods from java.lang.Object class and java.lang.Throwable class.

Hierarchy of NullPointerException

When NullPointerException throw

NullPointerException throw when a method called by null object.

For example, calling length() method on null string

String name=null;

System.out.println(name.length());//NullPointerException

Example:

package com.exceptions;

public class NullPointerExceptionTest {

       void message(){

              System.out.println("Hello World");

       }

       public static void main(String[] args) {       

              NullPointerExceptionTest obj=null;

              obj.message();            

       }

}

Output:

Exception in thread "main" java.lang.NullPointerException

       at com.exceptions.NullPointerExceptionTest.main(NullPointerExceptionTest.java:8)

Internal code of NullPointerException from java api  

package java.lang;

public class NullPointerException

  extends RuntimeException

{

  private static final long serialVersionUID = 5162710183389028792L;

 

  public NullPointerException() {}

 

  public NullPointerException(String paramString)

  {

    super(paramString);

  }

}

It has no argument constructor and one String argument constructor.