New to Java

I had written 2 classes and there output is also given. i would like to know the reason for null and any modification which i can do to get the value from map.

public class TestBean {

	String str=null;
	TestBean(String str)
	{
		this.str=str;
	}
}


public class Test {
	public static void main(String[] args) {
		Map map = new HashMap();
		TestBean t = new TestBean("junk");

		map.put(t, "buster");
		System.out.println(map.get(t));

		map.put(new TestBean("junk"), "buster");
		System.out.println(map.get(new TestBean("Harsh")));
	}
}

OUTPUT
buster
null

Edited by: EJP on 31/05/2011 17:31: corrected your title and added {noformat}

{noformat} tags