puzzling set behavior

[Ken Jones]

Here is a snippet of the relevant parts of some JUnit code that is puzzling me:

    import java.util.HashSet;
    import java.util.Set;
    import static org.junit.Assert.*;
    import org.junit.Test;

    public class PrecedenceRelationSet {
    
        private final Set<PrecedenceRelation> precedenceRelationSet = new HashSet<PrecedenceRelation>();
	
        public void add(PrecedenceRelation precedenceRelation) {
		precedenceRelationSet.add(precedenceRelation);
	}

	public int size() {
		return precedenceRelationSet.size();
	}	
    }

    @Test
    public void test() {
        // definition of precedenceRelation1 and precedenceRelation2 have been removed for clarity
        PrecedenceRelationSet precedenceRelationSet = new PrecedenceRelationSet();
	precedenceRelationSet.add(precedenceRelation1);
	precedenceRelationSet.add(precedenceRelation2);

	assertTrue(precedenceRelation1.equals(precedenceRelation2));
	assertTrue(precedenceRelationSet.size() == 2);
    }
    

This test passes, but I expect it to fail. I expect the size of the set to be 1 instead of two because I am adding two different objects that are equal to one another. I didn't think the second call to add() would add another member to the set because of this equality. What am I missing?

Thanks,

Ken

[Henry Wong]

Ken Jones wrote:This test passes, but I expect it to fail. I expect the size of the set to be 1 instead of two because I am adding two different objects that are equal to one another. I didn't think the second call to add() would add another member to the set because of this equality. What am I missing?

HashSet depends on the equals() and hashCode() method to determine equality -- so you need to show us the code for those two methods.

Henry

[Ken Jones]

While I was copying my code into this reply I found the source of my problem, in an equals() method, of course. Thanks for your help!

Ken