Add to Google Reader or Homepage

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.



 
java errors and exceptions © 2010 | Designed by Chica Blogger | Back to top