User Interaction

The example used the do in a counting loop. This was to show how it worked. Usually you would use a for loop. A better application of a do is where the user is repeatedly asked if the program should continue. The user is required to answer, so the loop body will execute at least once, so using a bottom-driven loop is safe.

import java.io.* ;
class SqrtCalc
{
  public static void main( String[] args )
      throws IOException
  {
    String chars;
    double x;
    BufferedReader stdin = new BufferedReader( 
        new InputStreamReader(System.in) );

    do
    {
      System.out.print("Enter a number-->");
      chars = stdin.readLine(); 
      x     = Double.parseDouble( chars );
      System.out.println("Square root of" + x +
          " is " + Math.sqrt( x ) );
      System.out.print("Do you wish to continue? (yes or no) -->");
      chars = stdin.readLine(); 

    }
    while ( chars.equals( "yes" ) );    

  }
}