How is order working in a Collection?

[Joey Sanchez]

This class is ordered by name but what does it happen when various objects have the same name?

public class MyStuff implements Comparable<MyStuff> {
	MyStuff(String n, int v){ name = n; value=v;}
	String name; int value;
	public int compareTo(MyStuff m){
		return name.compareTo(m.name);
	}
	public String toString() { return name + " " + value + " ";}
	public static void main(String[] args){
		List<MyStuff> l = new ArrayList<MyStuff>();
		MyStuff m0 = new MyStuff("hola",1);
		MyStuff m1 = new MyStuff("hola",1);
		MyStuff m2 = new MyStuff("hola",2);
		MyStuff m3 = new MyStuff("hola",2);
		l.add(m0);
		l.add(m1);
		l.add(m2);
		l.add(m3);
		Collections.sort(l);
		System.out.println(l);
		for(Object o: l) System.out.println(o.hashCode());
	}
}

Result:

[hola 1 , hola 1 , hola 2 , hola 2 ]
21722195
12719253
30758157
12773951

Which object is the first? Depends on value, hashcode..?

[Jeanne Boyarsky]

It depends on the original order of the list which affects the order compare to is run. In other words, you shouldn't rely on the order. It isn't guaranteed and future implementations of the JDK could change it.