CIS 260 AutoBox1.java

Code

/*
    AutoBox1.java
    CIS 260
    2/16/2005
    David Klick

    Demonstrates the new Java 1.5 autoboxing feature
    whereby Java automatically converts primitives
    into appropriate wrapper objects and vice versa..
*/

import java.util.*;

public class AutoBox1 {
    public static void main(String[] args) {
        // v.add() requires an Object reference
        //   Java does this conversion for us now
        //   Java also converts it back to an int
        //      when we add it to the accumulator
        Vector<Integer> v = new Vector<Integer>();
        for (int i=0; i<100; i+=10) v.add(i);
        int sum = 0;
        for (int j=0; j<v.size(); j++) {
            System.out.print(v.get(j) + "  ");
            sum += v.get(j);
        }
        System.out.println("\nSum = " + sum);

        // separate objects shouldn't test positive for equality
        //   - but there are exceptions!!!
        //   - don't depend on this behavior
        //   - don't forget about it either
        Integer i1 = new Integer(27);
        Integer i2 = new Integer(27);
        Integer i3 = 27;
        Integer i4 = 27;
        System.out.println("i1 == i2: " + (i1 == i2));
        System.out.println("i1 == i3: " + (i1 == i3));
        System.out.println("i1 == 27: " + (i1 == 27));
        System.out.println("i3 == i4: " + (i3 == i4));

        Integer i5 = new Integer(270);
        Integer i6 = new Integer(270);
        Integer i7 = 270;
        Integer i8 = 270;
        System.out.println("i5 == i6: " + (i5 == i6));
        System.out.println("i5 == i7: " + (i5 == i7));
        System.out.println("i5 == 27: " + (i5 == 27));
        System.out.println("i7 == i8: " + (i7 == i8));
    }
}
/*
    Sample output:

    0  10  20  30  40  50  60  70  80  90
    Sum = 450
    i1 == i2: false
    i1 == i3: false
    i1 == 27: true
    i3 == i4: true
    i5 == i6: false
    i5 == i7: false
    i5 == 27: false
    i7 == i8: false
*/