Using Lists/ArrayLists, code doesn't work

[David Pountney]

Hello,

I'm trying to pass a Model (the name of a class) into a method but I'm not getting any results, here is the code;

import java.awt.*;
import javax.swing.*;
import javax.swing.event.ChangeListener.*;
import java.awt.event.*;
import java.util.*;
public class Test {
static java.util.List<Model> player1models = new ArrayList<Model>();
public static void main(String [ ] args) {
for (int i=0; i < 10; i++) {
player1models.add(new Model("Bad lad","Shank",i));
}
}
public int closeCombatHitting(Model player1, Model player2) {
int hit = 0;
if (player1.WS > player2.WS) {
hit ++;
System.out.println("1");
}
else {
//do nothing
}
if (player1.WS < player2.WS) {
hit ++;
System.out.println("1");
}
else {
//do nothing
}
return hit;
}
}

The output I get is nothing, when it should just generate 10 number 1's. As the player1 and player 2 WS variable values are different. I've tracked the problem down to the "If player1.WS > player2.WS" line in the code, I'm not sure why it doesn't make a comparrison between the two different instances of the Model class.

Can anyone please suggest why my code isn't working as I expected?

Thanks

[Matthew Brown]

Based on that code, I wouldn't expect any output. You just add the models to the list - you don't do anything with them. Is there something missing?

[David Pountney]

Oh dear, Just made an epic fail.

I didn't call the method...

Thanks for pointing that out to me, I'll get back to you if the problem I mentioned keeps happening.

[Dawid Skrzypczynski]

Hi,

I think that you should use to compare object the Comparable Interface.

Look here:
Inteface

[David Pountney]

I called the method that outputs (using System.out.println) text on the screen but still I don't get anything, any ideas why?

Here is is the slightly updated code;

import java.awt.*;
import javax.swing.*;
import javax.swing.event.ChangeListener.*;
import java.awt.event.*;
import java.util.*;
public class Test {
static java.util.List<Model> player1models = new ArrayList<Model>();
public static void main(String [ ] args) {
for (int i=0; i < 10; i++) {
player1models.add(new Model("Bad lad","Shank",i));
}
for (int i=0; i < 10; i++) {
closeCombatHitting(player1models.get(i),player1models.get(i));
}
}
public static int closeCombatHitting(Model player1, Model player2) {
int hit = 0;
if (player1.WS > player2.WS) {
hit ++;
System.out.println("1");
}
else {
//do nothing
}
if (player1.WS < player2.WS) {
hit ++;
System.out.println("1");
}
else {
//do nothing
}
return hit;
}
}

Thanks again

[Matthew Brown]

You're passing the same Model object to closeCombatHitting for both parameters. Which means that player1 == player2, so neither test will work.

I don't quite know what you're intending to happen, but maybe you need something like this?

for (int i = 0; i < player1models.size() - 1; i++) {
closeCombatHitting(player1models.get(i), player1models.get(i + 1));
} 

[David Pountney]

Thanks for pointing that out, I've corrected it and my program does what I wanted it to do.

Just so I know, would this be a good way to remove the last element in a list?

player2models.remove(player2models.size()-1);