contains() method in List not working as expected

Question

the api of contains() method says

\"Returns true if this list contains the specified element. More formally, returns true if and only if this list conta

Answer 1

You overloaded equals instead of overriding it. To override Object's equals method, you must use the same signature, which means the argument must be of Object type.

Change to:

@Override
public boolean equals(Object other){
    if (!(other instanceof Animal))
        return false;
    Animal otherAnimal = (Animal) other;
    return (this.legs==otherAnimal.legs) && 
           (this.getClass().getName().equals(otherAnimal.getClass().getName()));
}

Answer 2

As JLS-8.4.8.1 specify

An instance method m1, declared in class C, overrides another instance method m2, declared in class A , if all of the following are true:

C is a subclass of A.

The signature of m1 is a subsignature  of the signature of m2.

Either:

m2 is public, protected, or declared with default access in the same package as C, or

m1 overrides a method m3 (m3 distinct from m1, m3 distinct from m2), such that m3 overrides m2.

Signature Must be same to override which in your case is ignored !!!