Java ArrayList IndexOf - Finding Object Index

Question

Lets say I have a class

public class Data{
    public int k;
    public int l;
    public Data(int k, int l){
      this.k = k; 
      this.l = l;
    }
             


        

Answer 1

The signature of your equals method is wrong. You are not overriding the equals in Object, but just overloading it.

To override the behavior of equals method in Object, your signature must exactly match with the one in Object. Try this:

public boolean equals(Object o) {
    if(!(o instanceof Data)) return false;
    Data other = (Data) o;
    return (this.k == other.k && this.l == other.l);
}

In addition, as others suggested, it is a good idea to override hashCode method also for your object to work correctly in map based collections.