Java program to demonstrate the use of try and catch blocks

NullPointerException

GD.java

class GD
{
    public static void main(String args[])
    {
        String s=null;
        System.out.println("Length: "+s.length());
    }
}

Output

godarda@gd:~$ javac GD.java
godarda@gd:~$ java GD
Exception in thread "main" java.lang.NullPointerException
    at GD.main(GD.java:6)
godarda@gd:~$

Java program to demonstrate the use of try and catch blocks

GD.java

class GD
{
    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

godarda@gd:~$ javac GD.java
godarda@gd:~$ java GD
String is null, hence, Unable to find the length.
godarda@gd:~$

Java program to demonstrate the use of try with multiple catch blocks

GD.java

class GD
{
    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

godarda@gd:~$ javac GD.java
godarda@gd:~$ java GD
Exception caught in the second catch block
godarda@gd:~$

Java program to handle the NullPointerException using Exception class

GD.java

class GD
{
    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

godarda@gd:~$ javac GD.java
godarda@gd:~$ java GD
Exception caught in the third catch block
godarda@gd:~$

Java program to handle the NullPointerException using RuntimeException class

GD.java

class GD
{
    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

godarda@gd:~$ javac GD.java
godarda@gd:~$ java GD
Exception caught in the second catch block
godarda@gd:~$

The following sequence of multiple catch blocks are not allowed

GD.java

class GD
{
    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

godarda@gd:~$ javac GD.java
godarda@gd:~$ java GD
GD.java:14: error: exception RuntimeException has already been caught
        catch(RuntimeException e)
        ^
GD.java:18: error: exception ArithmeticException has already been caught
        catch(ArithmeticException e)
        ^
2 errors
godarda@gd:~$

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

GoDarda

Java Programming