Question 3 ( 20 points ).

The classes My_int and CUCSApplication are defined on the next page. Each object of class My_int encapsulates an integer value in a field named x, i.e., each My_int is an object version of an integer.

For example,

My_int p = new My_int( 3 );

System.out.println( p.x );

would print 3.

( a ) Complete the implementation of the My_int constructor and the method add.

( b ) Show the output of executing CUCSApplication.main in the table below:

Output:

a= 20 b= 10

c= 30 d= 40

e= [60] f= [50]

true

e.x= 60 old_e.x= [60]

g + h= [150]

import java.io.*;

// My_int is a class representing integers as objects.

class My_int

{

public int x;

// Construct a My_int object with integer value x

My_int ( int x )

{

this.x = x;

}

static void swap2( My_int a, My_int b )

{

int temp = a.x; a.x = b.x; b.x = temp;

}

public String toString()

{

return "[" + x + "]";

}

//a.add(b) returns the sum of a and b's values as a My_int

public My_int add( My_int b )

{

return new My_-Int( x + b.x );

}

}

class CUCSApplication

{

static void swap1( int a, int b )

{

int temp = a; a = b; b = temp;

} // swap1

public static void main( String[] args )

{

// set a to 10, b to 20, "swap" a and b, and print a and b

int a = 10; int b = 20;

int temp = a; a = b; b = temp;

System.out.println( "a=" + a + " b=" + b );

// set c to 30, d to 40, "swap" c and d, and print c and d.

int c = 30; int d = 40;

swap1( c, d );

System.out.println( "c=" + c + " d=" + d );

// set e to 50, f to 60, "swap" e and f, and print e and f.

My_int e = new My_int( 50 );

My_int f = new My_int( 60 );

My_int old_e = e;

My_int.swap2( e, f );

System.out.println( "e=" + e + " f=" + f );

System.out.println( e == old_e );

System.out.println( "e.x= " + e.x + " old_e.x= " + old_e );

// set g to 7, h to 80, "add" g and h, and print their sum

My_int g = new My_int( 70 );

My_int h = new My_int( 80 );

System.out.println( "g + h= " + g.add( h ) );

}

} // CUCSApplication