Here is a unit test that illustrates the Fly Weight implementation of Integers in Java.

import junit.framework.TestCase;

public final class TestIntegers extends TestCase {
    public void testValueOfGivesTheSameIntegerForSmallValues() {
        assertSame(Integer.valueOf(1), Integer.valueOf(1));
    }

    public void testValueOfGivesADifferentIntegerForSomeValues() {
        assertNotSame(Integer.valueOf(13333333), Integer.valueOf(13333333));
        assertEquals(Integer.valueOf(13333333), Integer.valueOf(13333333));
    }

    public void testNew() {
        assertNotSame(new Integer(1), new Integer(1));
        assertEquals(new Integer(1), new Integer(1));
    }

    public void testValueOfGivesTheSameIntegerForAutoBoxing() {
        assertSame((Integer) 1, (Integer) 1);
    }

    public void testValueOfGivesADifferentIntegerForAutoBoxing() {
        assertNotSame((Integer) 13333333, (Integer) 13333333);
        assertEquals((Integer) 13333333, (Integer) 13333333);
    }
}

This entry was posted on Friday, April 23rd, 2010 at 6:00 am and is filed under Something for the week end. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.