LinkedHashSet is not Removing Duplicates

Question

I am using LinkedHashSet for removing duplicated entries. But for below custom model the Set still keeps duplicate entries. Please help me to find the bugs. Is there anything wrong with overriding equals method. For your kind information i only treats two node equals when their phone, type and status are same.

public class BlockNode { 
    public int id;
    public int type;
    public int status;
    public String phone;
    public String date;
    public String content;

    @Override
    public boolean equals(Object o) {
        return this.toString().equals(((BlockNode)o).toString());
    }

    @Override
    public String toString() {
        return "number:" + phone + " type:" + type + " status:" + status + "\n"; 
    }
}

In addition to overriding hashCode, also fix the implementation of equals(). It's not supposed to throw an exception if you pass an instance of another class, or null. It must return false in these cases. — JB Nizet, Jul 05 '14 at 08:52

score 7 · Accepted Answer · answered Jul 05 '14 at 08:50

7

You also have to override the method hashCode.

@Override
public int hashCode() {
    return toString().hashCode(); 
}

answered Jul 05 '14 at 08:50

nosid

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score 1 · Answer 2 · answered Jul 05 '14 at 08:50

1

Remember to override hashCode whenever you override equals.

answered Jul 05 '14 at 08:50

Henry

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what would be a good hashCode in this case. @Henry – Sazzad Hissain Khan Jul 05 '14 at 08:53
1

@Hissain: now is the time to start reading the javadoc of Object.equals() and Object.hashCode(), and figure that out by yourself. Also look at the `Objects` class – JB Nizet Jul 05 '14 at 08:54

LinkedHashSet is not Removing Duplicates

2 Answers2