Hashcode and equals

Question

equals and hashCode method must be consistent, which means that when two objects are equal according to equals method their hash

Answer 1

In the following code:

public boolean equals(Object oo) {
    if(oo instanceof Hashvalue) 
        HashValue hh = (HashValue) oo;

    if (this.x == hh.x)
        return true;
    else
        return false;
}

there are a couple of issue: 1. Hashvalue is not recognised by your compiler. It should be "HashValue" 2. hh is out of scope once out of if-block. Hence, compiler error.

You can change your program to following and it will work:

 public boolean equals(Object oo) {
     if(!(oo instanceof Hashvalue)) 
         return false;

     HashValue hh = (HashValue) oo;
     if (this.x == hh.x)
        return true;
     else
        return false;
}

or you can make it more concise as follows:

 public boolean equals(Object oo) {
     if(oo instanceof Hashvalue && this.x == ((HashValue) oo).x) 
         return true;
     return false;
}