Using compareTo and Collections.sort

Question

I have a franchise class with owner(owner of franchise's name), state(2-character string for the state where the franchise is located), and sales (total sales for the day)

public class Franchise implements Comparable <Franchise>  {
final String owner;
final String state;
final double sales;

protected Franchise(String owner, String state, double sales ) {
    this.owner = owner;
    this.state = state;
    this.sales = sales;
}
public String toString() {
    String str = state + ", " + sales + ", " + owner;
    return str;
}
public String getState() {
    return state;
}
public double getSales() {
    return sales;
}
public int compareTo(Franchise that) {
    double thatSales = that.getSales();
    if (this.getState().compareTo(that.getState()) < 0)  
        return -1;
    else if (this.getSales() > thatSales)
        return -1;
    else if (this.getSales() < thatSales)
            return 1;
    else
        return 0;
}
}

the compareTo is based on state ASCENDING and sales DESCENDING

import java.util.ArrayList;
import java.util.Collections;

public class FranchiseTester {

public static void main(String[] args) {
    ArrayList<Franchise> franchises = new ArrayList<Franchise>();
    Franchise a = new Franchise("Andrew Luck", "IN", 1270.5);
    Franchise b = new Franchise("Ray Rice", "MD", 1210);
    Franchise c = new Franchise("Alfred Morris", "WA", 980.5);
    Franchise d = new Franchise("Roddy White", "GA", 670);
    Franchise e = new Franchise("Greg Olsen", "SC", 740);
    Franchise f = new Franchise("T.Y. Hilton", "IN", 950);
    Franchise g = new Franchise("Julio Jones", "GA", 560);

    franchises.add(a);
    franchises.add(b);
    franchises.add(c);
    franchises.add(d);
    franchises.add(e);
    franchises.add(f);
    franchises.add(g);

    Collections.sort(franchises);

    for(int i = 0; i < franchises.size(); i++) {   
        System.out.print(franchises.get(i) + "\n");
    } 
}

}

when I compare these franchise objects without the Collections.sort they compare correctly, However when I test using the Collections.sort like I have here I get an output like this:

GA, 670.0, Roddy White
GA, 560.0, Julio Jones
IN, 1270.5, Andrew Luck
IN, 950.0, T.Y. Hilton
MD, 1210.0, Ray Rice
SC, 740.0, Greg Olsen
WA, 980.5, Alfred Morris

The state's are still being compared correctly but it's not comparing by sales properly (lower sales for particular stat should come first)

I think that the .sort compares string by default is the reason that states are still correct, my question is how do I implement it to compare based on sales too?

Solution 1

In your problem statement you are saying that "compareTo is based on state ASCENDING and sales DESCENDING". Based on this your results are valid. States are in ascending order and for each state the sale is in descending order. In the very next statement you are saying (lower sales for particular stat should come first). So basically you have two conflicting requirement. Both can not be done simultaneously.

In other words do you want your program to do something else like both should be ascending or both descending or some other order. If yes then you have to modify your compareTo method accordingly.

Solution 2

You have to modify your compareTo method. Cause you are returning after comparing the state. So you have to compare state but sales too.

For example:

public int compareTo(Franchise that) {
    int stateComparition = this.getState().compareTo(that.getState()); 
    Double sales = Double.valueOf(this.getSales());    
    Double thatSales = Double.valueOf(that.getSales());
    int salesComparition = sales.compareTo(thatSales);    

    if(stateComparition == 0){
        if(salesComparition > 0)
             return -1;
        else if(salesComparition < 0)
             return 1;
        else
             return 0;
    }
       return stateComparition;         
}

Comments

[nachokk]

@user2745043 here you are using string comparition and then if the string comparition is 0 then compare with sales, what is your problem?

[nachokk]

@user2745043 do you want first order by sales? and then with state?