java - 无法添加到 ArrayList

Question

我正在尝试迭代列表“breadthBoard”，并向其中添加一个数组“board”。但是，我添加到数组中的每个数组都会以某种方式变成原始数组，然后即使我已经测试了数组已更改，该数组也会被复制。

neighbourNodes 是一个列表，其中包含板上与当前节点相邻的所有值。

public List breadthBoard(List neighbourNodes, int [] currentNode, int [][] board)
{

    int x = currentNode[0] - 1; 
    int y = currentNode[1] - 1;
    //create lists
    List breadthBoard = new ArrayList();

for (int i=0; i<3;i++)
        {
            for(int j=0; j<3;j++)
            {

                if (neighbourNodes.contains(board[i][j]))
                {
                    // the temp variables allow me to switch the values then switch back later on
                    int temp = board[i][j];
                    int temp2 = board[x][y];
                    //initial switch
                    board[i][j] = temp2;
                    board[x][y] = temp;// at this point I get a successful swap but it isn't getting added to the breadth board
                    breadthBoard.add(board);

                    //test to see if I get the right results which I do
                    System.out.println("what's being added into breadth board (should be swapped)" + Arrays.deepToString(board)); 
                    System.out.println('\n');

                    switching the values back to the original postions
                    board[i][j] = temp;
                    board[x][y] = temp2;
                    System.out.print("back to normal " + Arrays.deepToString(board));// another test passed
                    System.out.println('\n');

                } 

            }

Answer 1

我做了一些测试。事实上，clone() 使用基本类型数组进行深度复制，但它与二维基本类型数组的工作方式不同。
对于二维数组，您应该迭代第一维并在第二维的 int[] 数组上执行 clone() :

   board[i][j] = temp2;
   board[x][y] = temp;

   //Here, I suppose that the second dimension has always the same size. 
   int[][] clonedBoard = new int[board[0].length][board[1].length];

   for (int t = 0; t < board.length; t++) {
     clonedBoard[t] = board[t].clone();
   }
   breadthBoard.add(clonedBoard);