NullPointerException
KW.java
class KW
{
    public static void main(String args[])
    {
        String s=null;
        System.out.println("Length: "+s.length());
    }
}
Output
kodingwindow@kw:~$ javac KW.java
kodingwindow@kw:~$ java KW
Exception in thread "main" java.lang.NullPointerException
    at KW.main(KW.java:6)
kodingwindow@kw:~$
Java program to demonstrate the use of try and catch blocks
KW.java
class KW
{
    public static void main(String args[])
    {
        String s=null;
        try
        {
            System.out.println("Length: "+s.length());
        }
        catch(Exception e)
        {
            System.out.println("String is null, hence, Unable to find the length.");
        }
    }
}
Output
kodingwindow@kw:~$ javac KW.java
kodingwindow@kw:~$ java KW
String is null, hence, Unable to find the length.
kodingwindow@kw:~$
Java program to demonstrate the use of try with multiple catch blocks
KW.java
class KW
{
    public static void main(String args[])
    {
        String s=null;
        try
        {
            System.out.println("Length: "+s.length());
        }
        catch(ArithmeticException e)
        {
            System.out.println("Exception caught in the first catch block");
        }
        catch(NullPointerException e)
        {
            System.out.println("Exception caught in the second catch block");
        }
        catch(Exception e)
        {
            System.out.println("Exception caught in the third catch block");
        }
    }
}
Output
kodingwindow@kw:~$ javac KW.java
kodingwindow@kw:~$ java KW
Exception caught in the second catch block
kodingwindow@kw:~$
Java program to handle the NullPointerException using Exception class
KW.java
class KW
{
    public static void main(String args[])
    {
        String s=null;
        try
        {
            System.out.println("Length: "+s.length());
        }
        catch(ArithmeticException e)
        {
            System.out.println("Exception caught in the first catch block");
        }
        catch(StringIndexOutOfBoundsException e)
        {
            System.out.println("Exception caught in the second catch block");
        }
        catch(Exception e)
        {
            System.out.println("Exception caught in the third catch block");
        }
    }
}
Output
kodingwindow@kw:~$ javac KW.java
kodingwindow@kw:~$ java KW
Exception caught in the third catch block
kodingwindow@kw:~$
Java program to handle the NullPointerException using RuntimeException class
KW.java
class KW
{
    public static void main(String args[])
    {
        String s=null;
        try
        {
            System.out.println("Length: "+s.length());
        }
        catch(ArithmeticException e)
        {
            System.out.println("Exception caught in the first catch block");
        }
        catch(RuntimeException e)
        {
            System.out.println("Exception caught in the second catch block");
        }
        catch(Exception e)
        {
            System.out.println("Exception caught in the third catch block");
        }
    }
}
Output
kodingwindow@kw:~$ javac KW.java
kodingwindow@kw:~$ java KW
Exception caught in the second catch block
kodingwindow@kw:~$
The following sequence of multiple catch blocks are not allowed
KW.java
class KW
{
    public static void main(String args[])
    {
        String s=null;
        try
        {
            System.out.println("Length: "+s.length());
        }
        catch(Exception e)
        {
            System.out.println("Exception caught in the third catch block");
        }
        catch(RuntimeException e)
        {
            System.out.println("Exception caught in the second catch block");
        }
        catch(ArithmeticException e)
        {
            System.out.println("Exception caught in the first catch block");
        }
    }
}
Output
kodingwindow@kw:~$ javac KW.java
kodingwindow@kw:~$ java KW
KW.java:14: error: exception RuntimeException has already been caught
        catch(RuntimeException e)
        ^
KW.java:18: error: exception ArithmeticException has already been caught
        catch(ArithmeticException e)
        ^
2 errors
kodingwindow@kw:~$
Comments and Reactions
What Next?
Java program to demonstrate the use of finally block Java program to demonstrate the use of nested try, catch, and finally blocks Java program to handle the ArithmeticException
Advertisement