Question

Say I have a class where I would have to check for multiple different types of objects. Would it be feasible/possible to override equals() in the following manner?

public boolean equals(Object o){
    if(o == null) return false;
    if(o instanceof class1){
        return this.class1.equals((class1) o);
    if(o instanceof class2){
        return this.class2.equals((class2) o);
    ...

}

Would this ever be useful? I assume here that I create a static overloaded equals() method in the respective classes (though maybe polymorphism would take care of that automatically as long as I cast?).

Answer 1

It seems like you want a method to check whether a specified object is equal to at least one of various member variables in the receiver.

It is inappropriate to override java.lang.Object#equals for this purpose.

You should instead provide a different method, e.g.

public boolean hasEquals(Object o) { // your impl }