maximal-rectangle Java code

Given a 2D binary matrix filled with 0’s and 1’s, find the largest rectangle containing all ones and return its area.

import java.io.*;import java.util.*;public class Solution {    public int maximalRectangle(char[][] matrix) {        if(matrix==null || matrix.length==0 || matrix[0].length==0)            return 0;        int max = 0;        int rows = matrix.length;        int cols = matrix[0].length;        int[] height = new int[cols];        int[] left = new int[cols];  //左边界(与高度相关进行判断)        int[] right = new int[cols]; //右边界        for(int i=0; i<cols; i++){            right[i] = cols;        }        for(int i=0; i<rows; i++){            int curLeft = 0;            int curRight = cols;   //当前左边界和右边界            //更新左边界            for(int j=0; j<cols; j++){                if(matrix[i][j] == '1'){                    height[j]++;                    left[j] = Math.max(curLeft, left[j]);                }else{                    height[j] = 0;                    curLeft = j+1;                    left[j] = 0;                }            }            for(int j=cols-1; j>=0; j--){                if(matrix[i][j]=='1'){                    right[j] = Math.min(curRight, right[j]);  //很重要的一步                }else{                    right[j] = cols;                    curRight = j;                }                //max = Math.max(max, (right[j]-left[j])*height[j]);            }            for(int k=0;k<cols;k++){                if(max<(right[k]-left[k])*height[k]){                    max=(right[k]-left[k])*height[k];                }            }        }        return max;    }}