为什么方法会更改布尔数组参数？

Question

我有一门课用来寻找穿过基本迷宫的路径。迷宫与起点和终点位置一起通过路径。我使用递归来找到点之间的路径。路径作为布尔数组返回。由于某种原因，传递给 Path() 的初始迷宫发生了变化。所以我尝试制作迷宫数组的副本以避免更改任何值，但它仍然无法正常工作。

为什么 path() 会改变 open[][]？可能是这里的 C 编程让我感到困惑。

public static boolean[][] path(boolean[][] open, 
                               int start_i, int start_j, 
                               int end_i, int end_j) 
{
    int n = open.length;
    boolean[][] openCopy = new boolean[n][n]; //make a copy of open

    for(int i = 0; i < n; i++)
    {
        for(int j = 0; j < n; j++)
        {
            openCopy[i][j] = open[i][j]; 
        }
    } 
    return findPath(openCopy, start_i, start_j, end_i, end_j);
}

public static boolean[][] findPath(boolean[][] openCopy, int start_i, int start_j, int end_i, int end_j) 
{
    boolean[][] path = new boolean[openCopy.length][openCopy[0].length];

    if(openCopy[start_i][start_j] == false) //return false if current position is not open
        return path;
    else
        openCopy[start_i][start_j] = false;  //make current position false if not (to prevent infinite backtracking)

    if(start_i == end_i && start_j == end_j) //if end found return true
    {
        path[start_i][start_j] = true;
        return path;
    }

    path = findPath(openCopy, start_i+1, start_j, end_i, end_j); // Move North
    path = findPath(openCopy, start_i, start_j+1, end_i, end_j); // Move East
    path = findPath(openCopy, start_i-1, start_j, end_i, end_j); // Move South
    path = findPath(openCopy, start_i, start_j-1, end_i, end_j); // Move West

    return path;
}

Answer 1

它没有，我知道这可能不是该方法的完全“适当”输入，但它证明了这一点：

public class MainForm {


public static void main(String[] args) {
    boolean[][] array = new boolean[][] {{false, false, true, false, false, false}, 
            {false, false, true, false, false, false}, 
            {false, false, true, false, false, false}, 
            {false, false, true, false, false, false}};

    boolean[] [] another = path(array, 0, 0, 3, 5);

    for (boolean[] bArray : array) {
        for (boolean b : bArray) {
            System.out.println(b);
        }
    }
    System.out.println("***********************");
    for (boolean[] bArray : another) {
        for (boolean b : bArray) {
            System.out.println(b);
        }
    }
}

public static boolean[][] path(boolean[][] open, int start_i, int start_j, int end_i, int end_j) {
    int n = open.length;
    boolean[][] openCopy = new boolean[n][n]; // make a copy of open

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            openCopy[i][j] = open[i][j];
        }
    }
    return findPath(openCopy, start_i, start_j, end_i, end_j);
}

public static boolean[][] findPath(boolean[][] openCopy, int start_i, int start_j, int end_i, int end_j) {
    boolean[][] path = new boolean[openCopy.length][openCopy[0].length];

    if (openCopy[start_i][start_j] == false) // return false if current position is not open
        return path;
    else
        openCopy[start_i][start_j] = false; // make current position false if not (to prevent infinite backtracking)

    if (start_i == end_i && start_j == end_j) // if end found return true
    {
        path[start_i][start_j] = true;
        return path;
    }

    path = findPath(openCopy, start_i + 1, start_j, end_i, end_j); // Move North
    path = findPath(openCopy, start_i, start_j + 1, end_i, end_j); // Move East
    path = findPath(openCopy, start_i - 1, start_j, end_i, end_j); // Move South
    path = findPath(openCopy, start_i, start_j - 1, end_i, end_j); // Move West

    return path;
}
}

输出

false
false
true
false
false
false
false
false
true
false
false
false
false
false
true
false
false
false
false
false
true
false
false
false
***********************
false
false
false
false
false
false
false
false
false
false
false
false
false
false
false
false

很明显，返回的数组和传入 path() 的数组内容不同，原始数组的原始值保持不变。我认为问题出在您的应用程序的其他地方。

Answer 2

我认为问题在于，您在内部 for 循环中传递引用。 试试这个：

for(int j = 0; j < n; j++)
        {
            openCopy[i][j] = open[i][j]; 
        }

这个：

for (int j = 0; j < n; j++) {
    openCopy[i][j] = new Boolean(open[i][j]);
}

我认为应该有帮助。