constructor running but not having a lasting effect

[J R Hatch]

I'd been wondering why no one was replying to my post asking this on Friday. Because I hadn't actually posted it might be a reason....

Anyway, so I 've written a class which should generate objects which take steps to run a session of a game. To test my code, I wrote a little class with a static main thread which would just try things out and print results. The constructor and fields for the game running class look like this:

 public class TsuroGameTracker {
public TsuroDeck deck;
public int numberOfPlayers;
public int turnCounter;
public TsuroPlayer[] playerList;
public TsuroPlayer[] initList;
public int[] gameBoard;
public boolean open;
public int dragonTile;
public TsuroGameTracker(String starterName, int starterColor) {
deck=new TsuroDeck();
int numberOfPlayers=1;
int turnCounter=0;
boolean open=true;
System.out.println("foo "+numberOfPlayers);
int dragonTile=-1;
playerList=new TsuroPlayer[8];
initList=new TsuroPlayer[8];
initList[0]=new TsuroPlayer(starterName,starterColor,0);
int[] gameBoard={36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36};
} 

and the little test program is

 class GameTest{
public static TsuroGameTracker game;
public static void main(String[] args) {
game=new TsuroGameTracker("Jon",0);
System.out.println("purple "+game.numberOfPlayers);
System.out.println(game.open);
game.addPlayer("Fred",12);
game.addPlayer("Susan",4);
game.addPlayer("Mark",2);
System.out.println(game.numberOfPlayers);
System.out.println(game.open);
System.out.println(game.initList[0].name);
System.out.println(game.initList[1].name);
System.out.println(game.initList[2].name);
System.out.println(game.initList[3].name);

So, if you follow my thinking (and assuming addplayer does what its name implies), it seems that the output should be something like

foo 1
purple 1
true
4
true
Jon
Fred
Susan
Mark

But instead, the output is

foo 1
purple 0
false
3
false
Fred
Susan
Mark


So... am I missing something obvious? Why does the testing program output a value of 1 for game.numberOfPlayers=0 when the constructor set numberOfPlayers=1?

Any ideas?

[Paul Clapham]

 

J R Hatch wrote:So... am I missing something obvious? Why does the testing program output a value of 1 for game.numberOfPlayers=0 when the constructor set numberOfPlayers=1?

I guess it isn't obvious, because a lot of Java beginners do the same thing. Your constructor assigns 1 to a local variable named "numberOfPlayers". It leaves the instance variable "numberOfPlayers" untouched because the local variable hides that.

So don't declare those local variables in your constructor. What you did for "playerList" is the right thing to do.

[Bear Bibeault]

Because this line:

 int numberOfPlayers=1; 

is creating a variable named numberOfPlayers in the constructor which occludes the instance variable.

[Edit: beat by 20 seconds!]

[J R Hatch]

 

Paul Clapham wrote:

J R Hatch wrote:So... am I missing something obvious? Why does the testing program output a value of 1 for game.numberOfPlayers=0 when the constructor set numberOfPlayers=1?

I guess it isn't obvious, because a lot of Java beginners do the same thing. Your constructor assigns 1 to a local variable named "numberOfPlayers". It leaves the instance variable "numberOfPlayers" untouched because the local variable hides that.

So don't declare those local variables in your constructor. What you did for "playerList" is the right thing to do.

You and Bear are awesome except for making me feel dumb. Thanks.