How to compare two object properties?

Question

public class CellAtt {
    private String brand;
    private long serial;
    private double price;

    public CellAtt(String brand, long serial, double price) {
        this.brand = brand;
        this.serial = serial;
        this.price = price;
    }
    public boolean Compare(Object c1,Object c2) {

    }

public class Main {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        CellAtt c1 = new CellAtt("nokia",4536895,3600.00);
        CellAtt c2 = new CellAtt("Samsung",4536895,3600.00);
    }
}

I have created two objects in main.java.

I want to compare two object properties, Brand and Price. If brand and price are the same, it must return true, or else false. Hope I'm clear.

This is from my assignments, the question is in this way.. "The design should allow for one cell phone to be compared to another cell phone for equality. Two cell phone objects are considered equal if they have the same brand and the same price." — Srjk, Jul 15 '17 at 04:39
Ok ok I get it now. You are asking something like this `obj1.price == obj2.price` and `obj1.brand.equals(obj2.brand)`. Since your attributes are `private`, you have implemented a method and you do not know how to implement that method. Is that the question? — Blasanka, Jul 15 '17 at 04:42
No, They are two objects if the brand of object 1 is equal to brand of object 2 then true and same procedure follows with the price — Srjk, Jul 15 '17 at 04:46

score 0 · Answer 1 · edited Jul 15 '17 at 06:16

0

In your Compare method:

public boolean Compare(Object c1,Object c2){
   c1 = (CellAtt)c1;
   c2 = (CellAtt)c2; 
}

method return true if c1.brand.equals(c2.brand) && c1.price == c2.price else return false.

Alternatively, you can override equals() method of Object class

edited Jul 15 '17 at 06:16

sfjac

6,386
4
42
62

answered Jul 15 '17 at 04:20

Isha Agarwal

420
4
11

Don't compare strings with "==".　`Object c1` has no field `brand` or `price`. – saka1029 Jul 15 '17 at 04:30
Yes got my mistake, Thank you. – Isha Agarwal Jul 15 '17 at 04:34

score 0 · Answer 2 · answered Jul 15 '17 at 04:24

0

The best way to tackle this problem would be to override the Object.equals() function which is built for this very specific purpose. More details cand be found here: https://www.tutorialspoint.com/java/lang/object_equals.htm

answered Jul 15 '17 at 04:24

Ashwin.S.M

5
5

Blasanka · Answer 3 · 2017-07-15T11:28:35.517

Best and good way to do this is, override the equals() method in Object class:

public boolean equals(Object c){
    if (c == null)
        return false;

    if (!CellAtt.class.isAssignableFrom(c.getClass()))
        return false;

    CellAtt obj = (CellAtt) c;

    return this.brand.equals(obj.brand) && this.price == obj.price;
}

read this to understand how to override equals() in Object class?

If you strictly want to implement a method by yourself do this:

Modify the compare() in CellAtt class.

public boolean compare(CellAtt c){
    if (c == null)
        return false;

    return this.brand.equals(c.brand) && this.price == c.price;
}

Then in the Main class, you can invoke the method like below:

boolean res = c1.compare(c2);
System.out.println(res);//this is added to check output

UPDATE

Comlete code:

CellAtt class:

public class CellAtt {
    private String brand;
    private long serial;
    private double price;

    public CellAtt(String brand, long serial, double price) {
        this.brand = brand;
        this.serial = serial;
        this.price = price;
    }

    @Override
    public boolean equals(Object c){
        if (c == null)
            return false;

        if (!CellAtt.class.isAssignableFrom(c.getClass()))
            return false;

        CellAtt obj = (CellAtt) c;

        return this.brand.equals(obj.brand) && this.price == obj.price;
    }

    //public boolean compare(CellAtt c){
    //    if (c == null)
    //        return false;
    //
    //    return this.brand.equals(c.brand) && this.price == c.price;
    //}
}

Main class:

public class Main {
    public static void main(String[] args) {
        CellAtt c1 = new CellAtt("nokia",4536895,3600.00);
        CellAtt c2 = new CellAtt("samsung",4536895,3600.00);

        boolean res = c1.equals(c2);
//      boolean res = c1.compare(c2);
        System.out.println(res);
    }
}

I'm getting this error " the method compare(CellAtt) is undefined for type CellAtt — Srjk, Jul 15 '17 at 05:20
check the argument data type, or may be spell mistake. copy and paste this and see, it is worked or not. — Blasanka, Jul 15 '17 at 05:25
@SreemanJuvvadi glad to help. So you can accept this answer. It will help who find answers to the question like this. — Blasanka, Jul 15 '17 at 05:47

score -1 · Answer 4 · edited Jul 15 '17 at 09:55

-1

public boolean Compare(Object c1,Object c2) {
    return c1.brand == c2.brand && c1.price == c2.price;
}

edited Jul 15 '17 at 09:55

xlm

4,594
13
42
47

answered Jul 15 '17 at 04:31

Nonsouris

3
3

anil_g · Answer 5 · 2017-07-15T05:44:20.337

-1

public  boolean Compare(Object c1, Object c2) {

        if(c1 == null || c2 == null)
            return false;

        CellAtt ca1=(CellAtt)c1;
        CellAtt ca2=(CellAtt)c2;

        if(ca1.brand.equals(ca2.brand) && ca1.price == ca2.price)
            return true;

    return false;
}

edited Jul 15 '17 at 05:44

answered Jul 15 '17 at 04:33

anil_g

54
1
8

How to call Campare method in Main.java ? – Srjk Jul 15 '17 at 04:58
new CellAtt().Compare(c1,c2); – anil_g Jul 15 '17 at 05:17

score -1 · Answer 6 · answered Jul 15 '17 at 04:34

public class CellAtt {
    private String brand;
    private long serial;
    private double price;

    public CellAtt(String brand, long serial, double price) {
        this.brand = brand;
        this.serial = serial;
        this.price = price;
    }

    @Override
    public int hashCode() {
        int hash = 42;
        hash = 29 * hash + Objects.hashCode(this.brand);
        hash = 29 * hash + (int) (this.serial ^ (this.serial >>> 32));
        return hash;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        final CellAtt other = (CellAtt) obj;
        if (this.serial != other.serial) {
            return false;
        }
        if (!Objects.equals(this.brand, other.brand)) {
            return false;
        }
        return true;
    }

}

How to compare two object properties?

6 Answers6

UPDATE