带程序的嵌套循环，布尔数组？

Question

In the constructor of the model class, I need to allocate the memory of this array of booleans (boolean[ ][ ] is_hidden;). I also need to set them to true, but have no idea how this happens, a nested loop will have to be used like the one in the paint method at he bottom, in order to set each element.

class MineFinderModel {
public static int MINE_SQUARE = 10;
public static int EMPTY_SQUARE = 0;

int num_of_cols;
int num_of_rows;
int[][] the_minefield;
boolean[][] is_hidden;

public MineFinderModel(int n_cols, int n_rows) {
    num_of_rows = n_rows;
    num_of_cols = n_cols;
    the_minefield = new int[num_of_cols][num_of_rows];
    is_hidden = new boolean[][];
}

Paint method example:

                   for (int i = 0;i<numCols;i++)
         {
        for(int j = 0;j<numRows;j++)
        {
            Rectangle r = getRect(i,j);
            g.setColor(Color.black);
            g2.draw(r);

            if(i==0&&j==0)                                  {
                g2.drawOval(x,y,w,h);
            g2.fillOval(x,y,w,h);
            }
            if(i==0&&j==(numRows-1))
            g2.fillOval(x,y,w,h);

            if(i==(numCols-1)&&j==0)
            g2.fillOval(x,y,w,h);

            if(i==(numCols-1)&&j==(numRows-1))
            g2.fillOval(x,y,w,h);

Answer 1

You need to define the array with the sizes eg

is_hidden = new boolean[cols][rows]();

and iterate through, setting each cell to true (booleans, and boolean arrays, default to false ).

Note that Arrays.fill() exists, but will only get you halfway, since it won't fill multidimensional arrays. You can use this, but you'd have to iterate through the rows, and use Arrays.fill on each row. Perhaps not worthwhile in this example, but worth being aware of regardless.

Answer 2

Try this:

    int num_of_cols = 2;
    int num_of_rows = 3;
    boolean[][] is_hidden;
    is_hidden = new boolean [num_of_cols][num_of_rows];

    for (int i = 0; i < num_of_cols; i++) {
        for (int j = 0; j < num_of_rows; j++) {
            is_hidden[i][j] = true;
        }
    }

You can see it is now correctly initialized:

    for (boolean[] col : is_hidden) {
        for (boolean elem  : col) {
            System.out.println(elem);
        }
    }

Answer 3

when you define a boolean array the value of all the elements are false by default. I would suggest instead of looping through all the elements, implement your conditions in way that you can use the default false value.

Eg.

boolean[][] isEnabled =  new boolean[10][10];
// code to set all elements to true
if(isEnabled[i][j]){
    //some code
}

this can be easily replaced by

boolean[][] isDisabled =  new boolean[10][10];
if(! isDisabled[i][j]){
    //some code
}

You can save processing time this way and code looks neat :).

Answer 4

Simply write a nested loop.

for (int i = 0;i<n_rows;i++){
    for(int j = 0;j<n_cols;j++){
        is_hidden[n_rows][n_cols] = true;
    }
}

Answer 5

我为您提供了一个简单的解决方案：与其使用数组is_hidden而不是用true填充它的每个元素，而是使用名称isVisible，并且根本不填充它，因为它的每个元素都已经初始化为false;）