public static void main(String[] args) {

char[][] matrix = {{'1','0','1','0','0'},{'1','0','1','1','1'},{'1','1','1','1','1'},{'1','0','0','1','0'}};

System.out.println(maximalSquare(matrix));

}

public static int maximalSquare(char[][] matrix) {

if(matrix.length==0) return 0;

int[][] dp = new int[matrix.length][matrix[0].length];

int max = 0;

for (int i = 0; i < matrix.length ; i++) {

for (int j = 0; j < matrix[0].length ; j++) {

if(i==0 || j==0) {

dp[i][j] = matrix[i][j]-'0';

max = Math.max(dp[i][j],max);

}

else{

if(matrix[i][j]=='1') {

dp[i][j] = Math.min(Math.min(dp[i - 1][j], dp[i][j - 1]), dp[i - 1][j - 1]) + 1; //dp[i][j] 最大正方形边长

max = Math.max(dp[i][j], max);

}

}

}

}

return max*max;

}