//------------
// Introduction to Programming Using Java: An Object-Oriented Approach
//	Arnow/Weiss
//------------
import java.awt.*;
import java.awt.event.*;
import java.applet.*;

class LifeThread extends Thread {
    public LifeThread(LifeDisplay lifeDisplay, int size) {
        this.lifeDisplay = lifeDisplay;
        world = new boolean[size][size];
        for (int i = world.length*4/10; i < 
             world.length*6/10; i++)
           for (int j = world.length*4/10; j < 
                world[i].length*6/10; j++)
           world[i][j] = true;
    }
    public void run() { // was doGenerations
        amRunning = true;
        amStopped = false;
        lifeDisplay.displayWorld(world);
        while (!amStopped && !lifeIsExtinct()) {
           try {
               Thread.sleep(25);
           } catch (Exception e) {}
           if (!amStopped && amRunning)
               nextGeneration();
           if (!amStopped && amRunning)
               lifeDisplay.displayWorld(world);
        }
    }
    public void ourStop() {
        amStopped = true;
    }
    public void ourSuspend() {
        amRunning = false;
    }
    public void ourResume() {
        amRunning = true;
    }
    private boolean lifeIsExtinct() {
        for (int i = 0; i < world.length; i++)
           for (int j = 0; j < world[i].length; j++)
               if (world[i][j])
                   return false;
        return true;
    }
    private void nextGeneration() {
        boolean[][]     newWorld = 
                  new boolean[world.length][world.length];
        for (int i = 0; i < world.length; i++)
           for (int j = 0; j < world[i].length; j++) {
               int x = livingNeighbors(i, j);
               newWorld[i][j] = MinNeighbors <= x  &&  x <= 
                                              MaxNeighbors;
           }
        world = newWorld;
    }
    private int livingNeighbors(int i, int j) {
        int result = 0;
        if (isAlive(i-1, j-1)) result++;
        if (isAlive(i-1, j)) result++;
        if (isAlive(i-1, j+1)) result++;
        if (isAlive(i, j-1)) result++;
        if (isAlive(i, j+1)) result++;
        if (isAlive(i+1, j-1)) result++;
        if (isAlive(i+1, j)) result++;
        if (isAlive(i+1, j+1)) result++;
        return result;
    }
    boolean isAlive(int i, int j) {
        if (i >= 0 && i < world.length &&
               j >= 0 && j < world[i].length &&
               world[i][j])
           return true;
        else
           return false;
    }
    boolean amRunning, amStopped;
    boolean[][] world;
    LifeDisplay lifeDisplay;
    static final int MinNeighbors = 2, MaxNeighbors = 3;
}