CODEWITHSUNDEEP
javahashmap
Bibin Mathew
Bibin Mathew

Reputation: 213

Maps and custom objects in java

I am trying the below piece of code.

class dog{
    private String name;
    public dog(String n){
        name = n;
    }
    public String getname(){ return name; }
    public void setname(String n){ name =n;}
    public boolean equals(Object o){
        //if (( o instanceof dog )&& (((dog)o).name == name)) return true;
        if (( o instanceof dog )&& (((dog)o).name.equals(name))) return true;
        else return false;
    }

    public int  hashcode(){
        return name.length();
    }
    public String toString(){
        return "Name:"+name;
    }
}

This is my Dog class . Now in Main method , I am trying to do the following 

Map<Object,Object> m = new HashMap <Object, Object>();

dog p = new dog("GM");
dog q = new dog ("GM");
System.out.println(p.equals(q));
m.put ( new dog("GM"),"K2"); 

System.out.println(m.get(new dog("GM")));

I am getting a true and a null value. i Was expecting a K2 instead of null . Can somebody help me with this . I have overridden hashcode and equals methods . What is the thing i am missing ??

EDIT : - Changed equals function. Same results .

Upvotes: 0

Views: 1796

Answers (1)

Kevin
Kevin

Reputation: 56059

The immediate problem is that hashCode needs a capital C, you are implementing hashcode with a lowercase c.

((dog)o).name == name compares the identities of the strings. That means if you have two instances of the string "GM", they will .equals() each other, but not ==.

Upvotes: 3

Related Questions