Exception in thread main java.lang.NullPointerException

Null Pointer Exception:

The NullPointerException would be thrown if a variable with null value is used in the statements in the program before assigning it a legitimate value.So whenever a variable is used in the program it should be given a value before using it.

Example1:

public class Nullpointer

{

public static void main(String args[])

{

String name=null;

check(name);

}

public static void check(String s)

{

if(s.equals("ram"))

System.out.println("granted access");

}

}

Error

Exception in thread "main" java.lang.NullPointerException

        at Nullpointer.check(Nullpointer.java:11)

        at Nullpointer.main(Nullpointer.java:6)

This exception is thrown because the string object is not assigned a legitimate value before using in the if conditional statement.

Example2:

public class Nullpointer

{

public void call()

{

String name=null;;

check(name);

}

public  void check(String s)

{

if(s.equals("ram"))

System.out.println("granted access");

}

}

public class Temp

{

public static void main(String args[])

{

Nullpointer np=null;

np.call();

}

}

Error:

Exception in thread "main" java.lang.NullPointerException

        at Temp.main(Temp.java:6)

In the above shown code this error was thrown because the object of Nullpointer is not defined with a legitimate value.Thus a variable of any type must be given a reasonable value before using it otherwise this error would be thrown.