Java textField无限循环

Question

Game class:

import java.util.Random;

public class Game {
public static void main(String args[]){

    //----------Sets up GUI----------

    GUI gameGUI = new GUI();
    gameGUI.setVisible(true);
    Player.setGUI(gameGUI);


    //----------Sets initial number of marbles, computer player and human player----------

    Random random = new Random();
    int initialNum;
    //loop makes sure initialNum of marbles is between 10 and 100
    do{                                 
        initialNum = random.nextInt(100);
    }while(initialNum < 10);
    //*****gameGUI.manageMarbles(initialNum, true);
    //end loop

    Pile pile = new Pile(initialNum);
    gameGUI.setPile(pile);

    int compChoice = random.nextInt(2) + 1; //number index (1 or 2) representing SIMPLE_COMPUTER or SMART_COMPUTER
    Player computer = new Player(Player.Type.values()[compChoice]);
    Player humanPlayer = new Player(Player.Type.HUMAN);


    //----------Game loop----------

    //Randomly determine first player
    Player currentPlayer;
    int playerIndex = random.nextInt(2); //will be used to determine next player in the loop
    if(playerIndex == 0){ currentPlayer = computer; }
    else { currentPlayer = humanPlayer; }

    //Loop
    while(pile.getNumMarbles() != 0){
        System.out.printf("%d marbles left.\n", pile.getNumMarbles());
        int removed = currentPlayer.playTurn(pile.getNumMarbles());
        pile.removeMarbles(removed);

        //Determine next player
        playerIndex = Math.abs(playerIndex - 1); //if playerIndex = 0, it becomes 1, and vice-versa
        if(playerIndex == 0){ currentPlayer = computer; }
        else { currentPlayer = humanPlayer; }

    }

    System.out.println(currentPlayer + " won");



}
}

Player class:

import java.util.Scanner;
import java.util.Random;
public class Player {

    public enum Type{HUMAN, SIMPLE_COMPUTER, SMART_COMPUTER}
    private Type type;
    static private GUI gui;

    public Player(Player.Type type){
         this.type = type;
    }

    public Player.Type getType(){
         return type;
    }

    public int playTurn(int pileSize){
          Random random = new Random();
          if(type == Type.HUMAN){

              int marbles;
          do{
             marbles = gui.getMarblesToRemove();
          }while(marbles < 0);
              return marbles;

          }

          else if(type == Type.SIMPLE_COMPUTER){
           if(pileSize == 1){
               return 1;
               }
           else{
           int remove = random.nextInt(pileSize/2) + 1;
               if(remove == (pileSize/2) + 1){ remove -= 1; }
               return remove;
               }
          }

          else if(type == Type.SMART_COMPUTER){ 
               if(pileSize == 1){
               return 1;
            }
               else if(pileSize == 3 || pileSize == 7 || pileSize == 15 || pileSize== 31 || pileSize== 63 || pileSize <= 3){
              int remove = random.nextInt(pileSize/2) + 1;
              if(remove == (pileSize/2) + 1){ remove -= 1; }
              return remove;
            }
           else{
               for(int i=1; i<=pileSize/2; i++){
                   int size = pileSize - i;
               if(size == 3 || size == 7 || size == 15 || size == 31 || size == 63){
                    return i;
                }
            }
        }
    }
    return 0;

   }


public String toString(){
    return ""+type;
}

public static void setGUI(GUI guii){
    gui = guii;
}


}

GUI class:

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JTextField;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class GUI extends JFrame {

  private JPanel panel;
  private JButton removeButton; //button to remove marbles
  private JTextField marblesAmount; //amount of marbles to remove
  private static final int FIELD_WIDTH = 2;
  private JLabel marblesLabel;
  private JLabel errorLabel;
  private Pile pile;
  private int marblesToRemove;
  private ClickListener listener;
  static final private int WIDTH = 700, HEIGHT = 600;

  public GUI(){
    super.setTitle("test");
    super.setSize(WIDTH, HEIGHT);
    super.setDefaultCloseOperation(EXIT_ON_CLOSE);
    panel = new JPanel();
    marblesLabel = new JLabel("How many marbles to remove?");
    errorLabel = new JLabel("");
    removeButton = new JButton("Remove");
    listener = new ClickListener();
    removeButton.addActionListener(listener);
    marblesAmount = new JTextField(FIELD_WIDTH);
    panel.add(removeButton);
    panel.add(marblesLabel);
    panel.add(marblesAmount);
    panel.add(errorLabel);
    super.add(panel);
    marblesToRemove = 0;
  }

  public void setPile(Pile pile){
    this.pile = pile;
  }



  private class ClickListener implements ActionListener{

    public void actionPerformed(ActionEvent event){
        marblesToRemove = Integer.parseInt(marblesAmount.getText());

    }
  }

  public int getMarblesToRemove(){
    return marblesToRemove;
  }


}

Pile Class:

public class Pile {

private int initialNum;
private int currentNum;

public Pile(int initialNum){
    setNumMarbles(initialNum);
    currentNum = initialNum;
}

public int getNumMarbles(){
    return currentNum;
}

public void removeMarbles(int numToRemove){
    currentNum = currentNum - numToRemove;
}

public void setNumMarbles(int amount){
    initialNum = amount;
}

public String toString(){
    return "Number of marbles: " + currentNum;
}

}

What I am trying to do is to get the function playTurn(int pileSize) in the Player class to return the variable marbles(inside the if(type == Type.HUMAN) block ) only when it is not zero. The variable marblesToRemove from the gui class is assigned to marbles, by calling the function getMarblesToRemove() .

marblesToRemove is initially set to 0 in the default constructor for the gui class, and that causes the functionplayTurn(int pileSize) to go in an infinite loop. But marblesToRemove is changed to another value that is input in a JTextField ( marblesAmount ) when aa button( removeButton ) is pressed. But the the do while loop will still be an infinite loop and the function will return nothing, why? Can someone please help? Thanks.

Answer 1

This is probably because of at least two issues that I can see. The first is that you are modifying the variable in one thread, and reading it in the other. This should be done using either synchronization, or some other locking mechanism (Lock or AtomicInteger, etc.).

The second issue is that your reading-thread should not be doing a 'tight' loop. This is bad practices that sends one CPU to 100% usage. It should be done using some form of notification. Again, synchronization comes to mind.

Until you fix these two issues, you will always have unreliable results.

For what it's worth, in your particular case, if I were to make an educated guess, I would guess that there are two important copies of the marblesAmount (and there are alsways multiple copies). There's the copy thati's in the L1 and registers of one CPU that's doing a tight loop waiting for that register to change, and the other is in another core on your CPU setting it to a new value. Unless you use some synchronization, or somethin from the java.util.concurrent.* library you ave no way to tell one copy of the variable to refresh the other.

Answer 2

I got it to work finally. I just added a line of code "System.out.print("");" in the do-while loop in the Player class.

So now it looks like

 do{
         marbles = gui.getMarblesToRemove();
         System.out.print("");
      }while(marbles < 0); 

I have no idea why that works, but it does lol. Now the function actually returns the value that I set in the JTextField if it is not zero.