岛屿的个数

public class  {
    
     * @param grid a boolean 2D matrix
     * @return an integer
     */
    public int numIslands(boolean[][] grid) {
        int count=0;
        for(int i=0;i<grid.length;i++){
            for(int j=0;j<grid[i].length;j++){
                if(grid[i][j]==true){
                    count++;
                    change(grid,i,j);
                }
            }
        }
        return count;
    }
    public void change(boolean[][] grid,int i,int j){
        grid[i][j]=false;
        if(i>0 && grid[i-1][j]==true){
            change(grid,i-1,j);
        }
        if(i<grid.length-1&&grid[i+1][j]==true){
            change(grid,i+1,j);
        }
        if(j>0&&grid[i][j-1]==true){
            change(grid,i,j-1);
        }
        if(j<grid[i].length-1&&grid[i][j+1]==true){
            change(grid,i,j+1);
        }
    }