题目：Longest Substring Without Repeating Characters 不重复的最长子串

难度：中等

Given a string, find the length of the longest substring without repeating characters.

Example 1:

Input: "abcabcbb"
Output: 3 
Explanation: The answer is "abc", with the length of 3. 

Example 2:

Input: "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

Input: "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3. 
             Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

题意解析：

给定一个字符串，找出其中最长的不重复子串。

解题思路一：

循环遍历所有的子字符串，获取最长的子字符串。

public int lengthOfLonges