无重复字符最长子串

import java.util.*;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        //while (in.hasNextInt()) { // 注意 while 处理多个 case
        //int a = in.nextInt();
        //int b = in.nextInt();
        //System.out.println(a + b);
        //}
        while (in.hasNext()) {
            String a = in.next();
            int maxLength = 0;
            Map<String, Integer> map = new HashMap<String, Integer>();
            for (int i = 0, j = 0; i < a.length() && j < a.length(); j++) {
                if (map.get(a.substring(j, j + 1)) != null) {
                    if (i < map.get(a.substring(j, j + 1)) + 1) {
                        i = map.get(a.substring(j, j + 1)) + 1;
                    } else {
                        if (maxLength < j - i + 1) {
                            maxLength = j - i + 1;
                        }
                    }
                } else {
                    if (maxLength < j - i + 1) {
                        maxLength = j - i + 1;
                    }
                }
                map.put(a.substring(j, j + 1), j);
            }
            System.out.print(maxLength);
        }
    }
}