try{} and catch{}

To catch an exception:

1. Put code that might throw an exception inside a try{} block.
2. Put code that handles the exception inside a catch{} block.

Here is the example program with code added to do this:

import java.util.* ;

public class SquareFix 
{

  public static void main ( String[] a ) throws IOException
  {
    Scanner scan = new Scanner( System.in  );
    int num ;

    System.out.print("Enter an integer: ");

    try
    { 
      num    = scan.nextInt();      
      System.out.println("The square of " + num + " is " + num*num );
    } 

    catch ( InputMismatchException ex )
    { 
      System.out.println("You entered bad data." );
      System.out.println("Run the program again." );
    } 

    System.out.println("Good-by" );

  }
}

If a statement inside the try{} block throws a InputMismatchException, the catch{} block immediately starts running. The remaining statements in the try{} block are skipped. The reference variable ex refers to the Exception object. (However, this example does nothing with it.)

After the catch{} block is executed, execution continues with the statement that follows the catch{} block. Execution does not return to the try{} block.