What is the wrapper class for the primitive numeric type int?

A good answer might be:

Integer

(It would not be too surprising if you forgot that.) Here is a program that computes the square of a number that the user enters. It uses the one-line method of constructing a BufferedReader.

import java.io.*;
class EchoSquare
{
  public static void main (String[] args) throws IOException
  { 
    BufferedReader stdin = 
        new BufferedReader ( new InputStreamReader( System.in ) );
 
    String inData;
    int    num, square;                      // declaration of two int variables

    System.out.println("Enter an integer:");
    inData = stdin.readLine();
    
    num    = Integer.parseInt( inData );     // convert inData to int
    square = num * num ;                     // compute the square

    System.out.println("The square of " + inData + " is " + square );
  }
}

This program is the previous program with a few additions (in blue). You can copy-paste-and-run it. Better yet, study it for a while, then go to NotePad and see how much you can reconstruct. Now look at this statement:

    num    = Integer.parseInt( inData );     // convert inData to int

This uses the method parseInt() of the Integer wrapper class. This method takes a String containing an integer in character form. It looks at those characters and calculates an int value. That value is assigned to num.

QUESTION 15:

What would the following statement do?

    num    = Integer.parseInt( "39" );