class A {
    private int a;
    public A(int a) { this.a = a; }

    @Override
    public final boolean equals(Object o) {
        // Check if the exact classes are the same
        if (this.getClass() != o.getClass()) return false;
        return this.a == ((A) o).a;
    }
}

class B extends A {
    private int b;

    public B(int a, int b) { super(a); this.b = b; }
}

A a = new A(0);
B b = new B(0, 1);

System.out.println(a.equals(b)); // false
System.out.println(b.equals(a)); // false

System.out.println(a.equals(a)); // true
System.out.println(b.equals(b)); // true