Intersection of interval lists

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class  Intersection of interval list  {
    public static void main(String[] args) {
        int[][] firstList  = {
   {0,2},{5,10},{13,23},{24,25}};
        int[][] secondList = {
   {1,5},{8,12},{15,24},{25,26}};
        int[][] merge = intervalIntersection(firstList,secondList);
        for (int[] a:merge) {
            System.out.println(Arrays.toString(a));
        }
    }

    public static int[][] intervalIntersection(int[][] firstList, int[][] secondList) {
        int len1=firstList.length;
        int len2=secondList.length;
        if(len1==0 || len2==0)
            return new int[0][2];
        int i=0;
        int j=0;
        List<int[]> list=new ArrayList<int[]>();
        while (i<len1 && j<len2){
            int start=Math.max(firstList[i][0],secondList[j][0]);
            int end=Math.min(firstList[i][1],secondList[j][1]);
            if(start<=end)// If there is an intersection , Preservation 
                list.add(new int[]{start,end});
            if(firstList[i][1]<secondList[j][1])
                i++;
            else
                j++;
        }
        return list.toArray(new int[list.size()][2]);
    }
}
/*
 Given two by some   Closed interval   A list of components ,firstList  and  secondList , among  firstList[i] = [starti, endi]  and  secondList[j] = [startj, endj]
. Each interval list is paired   Disjoint   Of , also   It's sorted  . Back here   The intersection of two interval lists  .
 Formally , Closed interval  [a, b]（ among  a <= b） For real numbers  x  Set , and  a <= x <= b .
 Of two closed intervals   intersection   Is a set of real numbers , Or it's an empty set , Either it's a closed interval . for example ,[1, 3]  and  [2, 4]  The intersection of is  [2, 3] .
 Example  1：
 Input ：firstList = [[0,2],[5,10],[13,23],[24,25]], secondList = [[1,5],[8,12],[15,24],[25,26]]
 Output ：[[1,2],[5,5],[8,10],[15,23],[24,24],[25,25]]
 Example  2：

 Input ：firstList = [[1,3],[5,9]], secondList = []
 Output ：[]
 Example  3：

 Input ：firstList = [], secondList = [[4,8],[10,12]]
 Output ：[]
 Example  4：

 Input ：firstList = [[1,7]], secondList = [[3,10]]
 Output ：[[3,7]]
*/