overriding equal and hashcode in Java where this.obj is null

Question

Hi I am trying to overriding the equal and hashcode method in for my custom class .

here is my custom class

public class property
{
    public String type = null;
    public int value;
    public int id;
    public String name = null;
    public String course = null;



    public property(String type, String course, int value, int id)
    {
        this.value = value;
        this.type = type;
        this.course = course;
        this.id = id;
    }

    @Override
    public boolean equals(Object obj) {
        if(this == obj)
            return true;
        if((obj == null) || (obj.getClass() != this.getClass()))
            return false;

        property sig = (property) obj;

        if(sig != null) {
            if(sig.type.equals("EST1")) {
                if (sig.name != null && sig.type != null && sig.course != null) {
                    Log.d("property", "Other   " + sig.course + "AHHAHAHA " + course + "shahahaaha " + sig.id + "babababaab " + id);
                    if (sig.course.equals(this.course) && sig.value == this.value && sig.type.equals(this.type) && sig.id == (this.id)) {
                        Log.d("property", "EST1");
                        return true;
                    }

            }

        }
        return false;
}

The problem is that "this.id, this.type" is always null or 0 I do not understand why...while sig.id, sig.type have values. Just to let you know it is only code snippet, not full code so it might have typos and not logically correct..

Answer 1

Your code works well in my side, so I guess your test program is somewhat different (or complicated?) from mine.

I tried following for test,

property p = new property("a","b", 100, 200);
System.out.println("id:"+p.id);
System.out.println("type:"+p.type);
System.out.println(p.equals(p) +" should be true..");

And I got,

id:200
type:a
true should be true..