JAVA - 康威的生命游戏删除了所有活细胞？

Question

I am working on Conway's Game of Life for a school project. I am not looking for the code directly. I am looking to find out what is wrong with my code.

In Conway's Game of Life a cell goes from dead to alive if it has 3 alive neighbors. It stays alive if it has two or three alive neighbors. If none of those are true it is dead.

My LifeView class has a method that displays the cell simulation and afterwards displays how many alive cells are around the given point.

This is the output I am getting:

How many rows is your simulation?
5
How many columns is your simulation?
5
How many generations is your simulation?
3
xxxxx
xxxxx
xx0xx
xx0xx
xx0xx

00000
01110
02120
03230
02120


xxxxx
xxxxx
xxxxx
xxxxx
xxxxx

00000
00000
00000
00000
00000


xxxxx
xxxxx
xxxxx
xxxxx
xxxxx

00000
00000
00000
00000
00000

This is wrong because the second generation is supposed to be a horizontal line of live cells crossing the center of the first generation alive cells. Instead of crossing that center, all cells are turned dead. I am stumped as to why it doesn't work.

Main class:

package gameOfLife;

import java.util.Scanner;

public class Main {

/**
 * @param args the command line arguments
 */
public static void main(String[] args)
{
    Scanner numReader = new Scanner(System.in);
    System.out.println("How many rows is your simulation?");
    int rows = numReader.nextInt();
    System.out.println("How many columns is your simulation?");
    int columns = numReader.nextInt();
    System.out.println("How many generations is your simulation?");
    int generations = numReader.nextInt();


    LifeModel model = new LifeModel(rows,columns);
    LifeView life = new LifeView(model);

    for(int i=0; i<generations; i++)
    {
         life.displayLife();
         model.nextGeneration();
    }

}

LifeView class:

package gameOfLife;

import java.util.Scanner;

public class LifeView {

private LifeModel model;

public LifeView(LifeModel model)
{
    this.model = model;
}


public void displayLife()
{
    for(int i=0; i < model.getWorld().length; i++)
    {
        for(int j=0; j < model.getWorld()[0].length; j++)
        {

            if(model.getWorld()[i][j])
            {
                System.out.print("0");
            }
            else
            {
                System.out.print("x");
            }
        }
        System.out.println("");
    }
    System.out.println("");

    for(int i=0; i < model.getWorld().length; i++)
    {
        for(int j=0; j < model.getWorld()[0].length; j++)
        {

            System.out.print(model.numLivingNeighbors(i,j));
        }
        System.out.println("");
    }
    System.out.println("");
    System.out.println("");
}
}

LifeModel class: package gameOfLife;

public class LifeModel
{
private boolean[][] world;
private int numRows;
private int numCols;
private boolean[][] tempWorld;



public LifeModel(int rows, int cols)
{
    this.numRows=rows;
    this.numCols=cols;
    world = new boolean[rows][cols];
    initWorld();
    tempWorld = world;
}

private void initWorld()
{

    boolean done = false;

    while(!done)
    {
        int i = (int) (Math.random()*numRows);
        int j = (int) (Math.random()*numCols);
        if(j>0 && i>0 && i<numRows-1 && j<numCols-1)
        {
            /*
             world[i-1][j-1] = true;
             world[i-1][j] = true;
             world[i-1][j+1] = true;
             world[i][j+1] = true;
             world[i+1][j] = true;
             */
             world[i][j]=true;
             world[i+1][j]=true;
             world[i-1][j]=true;
             done = true;
        }
    }


}

public void nextGeneration()
{
    //tempWorld = new boolean[numRows+2][numCols+2];

    int rows = world.length;
    int columns = world[0].length;

    for(int i=0; i < rows; i++)
    {
        for(int j = 0; j < columns; j++)
        {
            toggleCell(i,j);
        }
    }
    world = tempWorld;
}

public void toggleCell(int r, int c)
{
    int count = numLivingNeighbors(r,c);
    if(!world[r][c] && count==3)
    {
        tempWorld[r][c] = true;
    }
    else if(world[r][c] && (count>=2 && count<=3))
    {
        tempWorld[r][c] = true;
    }
    else
    {
        tempWorld[r][c] = false;
    }
}

public int numLivingNeighbors(int r, int c)
{
    int count = 0;
    boolean newCells[][] = world;
    for(int i = -1; i<=1; i++)
    {
        for(int j = -1; j<=1; j++)
        {
            if(i!=0 || j!=0)
            {
                int row = r + i;
                int column = c + j;
                if(row>=0 && row < newCells.length && column>=0 && column<newCells[0].length && newCells[row][column])
                {
                    count++;
                }
            }
        }
    }
    return count;
}

public void userChange()
{

}

public boolean[][] getWorld()
{
    return world;
}


}

Any help is GREATLY appreciated!

Answer 1

You just have a couple small issues with your LifeModel class.

In your constructor you set the tempWorld to reference the same array as the actual game world. This will cause any modifications to tempWorld to also affect the gameWorld.

public LifeModel(int rows, int cols)
{
    this.numRows=rows;
    this.numCols=cols;
    world = new boolean[rows][cols];
    initWorld();
    //tempWorld = world;  // You can remove this line.
}

Then in next generation you have the line "//tempWorld = new boolean[numRows+2][numCols+2];" commented out. You really do need to create a new temp array here so you aren't changing the game board as you read it. However, I'm not sure what the +2 is supposed to be, so I removed it. You should have:

public void nextGeneration()
{
    tempWorld = new boolean[numRows][numCols]; // Keep it the same size

    int rows = world.length;
    int columns = world[0].length;

    for(int i=0; i < rows; i++)
    {
        for(int j = 0; j < columns; j++)
        {
            toggleCell(i,j);
        }
    }
    world = tempWorld;
}

After I made those changes it worked perfectly for me. I've included the full LifeModel class below that I used on my machine.

package gameOfLife;

public class LifeModel
{
private boolean[][] world;
private int numRows;
private int numCols;
private boolean[][] tempWorld;



public LifeModel(int rows, int cols)
{
    this.numRows=rows;
    this.numCols=cols;
    world = new boolean[rows][cols];
    initWorld();
}

private void initWorld()
{

    boolean done = false;

    while(!done)
    {
        int i = (int) (Math.random()*numRows);
        int j = (int) (Math.random()*numCols);
        if(j>0 && i>0 && i<numRows-1 && j<numCols-1)
        {
            /*
             world[i-1][j-1] = true;
             world[i-1][j] = true;
             world[i-1][j+1] = true;
             world[i][j+1] = true;
             world[i+1][j] = true;
             */
             world[i][j]=true;
             world[i+1][j]=true;
             world[i-1][j]=true;
             done = true;
        }
    }


}

public void nextGeneration()
{
    tempWorld = new boolean[numRows][numCols];

    int rows = world.length;
    int columns = world[0].length;

    for(int i=0; i < rows; i++)
    {
        for(int j = 0; j < columns; j++)
        {
            toggleCell(i,j);
        }
    }
    world = tempWorld;
}

public void toggleCell(int r, int c)
{
    int count = numLivingNeighbors(r,c);
    if(!world[r][c] && count==3)
    {
        tempWorld[r][c] = true;
    }
    else if(world[r][c] && (count>=2 && count<=3))
    {
        tempWorld[r][c] = true;
    }
    else
    {
        tempWorld[r][c] = false;
    }
}

public int numLivingNeighbors(int r, int c)
{
    int count = 0;
    boolean newCells[][] = world;
    for(int i = -1; i<=1; i++)
    {
        for(int j = -1; j<=1; j++)
        {
            if(i!=0 || j!=0)
            {
                int row = r + i;
                int column = c + j;
                if(row>=0 && row < newCells.length && column>=0 && column<newCells[0].length && newCells[row][column])
                {
                    count++;
                }
            }
        }
    }
    return count;
}

public void userChange()
{

}

public boolean[][] getWorld()
{
    return world;
}


}

Answer 2

Check that numLivingNeighbors is returning the proper value for each cell in the world.

Also check the step for staying alive

Answer 3

Hey You have done a simple mistake in your code

public LifeModel(int rows, int cols)
{
    this.numRows=rows;
    this.numCols=cols;
    world = new boolean[rows][cols];
    initWorld();
    tempWorld = world;
}

this is LifeModel constructor. In this constructor you need to initialize tempworld also. You should not assign your world to tempworld. After modification this block of code will become like this....

public LifeModel(int rows, int cols)
{
this.numRows=rows;
this.numCols=cols;
world = new boolean[rows][cols];
tempWorld = new boolean[rows][cols];
initWorld();
}

After this your output will be correct.