Java - equals method in base class and in subclasses

Question

I have a simple base class, which is later extended by many separate classes, which potentially introduce new fields, but not necessarily. I defined an equals method in the

Answer 1

While the following doesn't handle every case, I've found it to be quite practical. I've used this many times when I have both a SuperClass and a SubClass in play. I don't want to inter-compare them, but I also don't want to re-implement all of SuperClass equals() for SubClass. It handles:

• a.equals(b) == b.equals(a)
• Does not duplicate field comparison code
• Easily generalized for any subclass depth
• Subclass.equals(SuperClass) == false
• Superclass.equals(SubClass) == false

Code example

// implement both strict and asymmetric equality
class SuperClass {
   public int f1;
   public boolean looseEquals(Object o) {
      if (!(o instanceof SuperClass)) return false;
      SuperClass other = (SuperClass)o;
      return f1 == other.f1;
   }
   @Override public boolean equals(Object o) {
      return looseEquals(o) && this.getClass() == o.getClass();
   }
}
class SubClass extends SuperClass {
   public int f2;
   @Override public boolean looseEquals(Object o) {
      if (!super.looseEquals(o)) return false;
      if (!(o instanceof SubClass)) return false;
      SubClass other = (SubClass)o;
      return f2 == other.f2;
   }
   // no need to override equals()
}