java求字符串中的最长字串

package com.test;

import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

public class Test1 {

    public static void main(String[] args) {


        Scanner in=new Scanner(System.in);
        String s = in.next();
        System.out.println(getMaxlength(s));

    }

    public static int getMaxlength(String s) {
        if(s.length() <= 1) {
            return 1;
        }
        int sumCount = 0;
        int i = 0;
        int j = 0;
        int len = s.length();
        Set set = new HashSet<>();

        while(i < len && j < len) {
            if(!set.contains(s.charAt(j))) { 
                set.add(s.charAt(j++));
                sumCount = Math.max(sumCount, j - i);  //比较是现在子串的长度，和曾经最长字串的长度
            } else {
                set.remove(s.charAt(i++));    //如果出现相同元素，则减去最前面的字符
            }
        }

        return sumCount;

    }
}

做个笔记