override equals method to compare more than one field in java

Question

What is the best way to override equals method in java to compare more than one field? For example, I have 4 objects in the class, o1, o2, o3, o4 and I want compare all of t

Answer 1

Use a utility method to help you

private static boolean nullSafeEquals(Object o1, Object o2) {
    if(o1 == null && o2 == null) return true; // both null, both equal
    if(o1 == null || o2 == null) return false; // if one is null, not equal - we know both won't be null
    return o1.equals(o2);
}

public boolean equals(Object o) {
    if(o instanceof ThisClass) {
        ThisClass tc = (ThisClass)o;
        return nullSafeEquals(o1, tc.o1)
            && nullSafeEquals(o2, tc.o2)
            && nullSafeEquals(o3, tc.o3)
            && nullSafeEquals(o4, tc.o4);
    }
    return false;
}