java截取含有汉字的字符串

package com.test;public class Str {public static void main(String[] args) {String str1 = "我ABC";String str2 = "我ABC汉DEF";System.out.println(new Str().sub(str1, 4));System.out.println(new Str().sub(str2, 6));}public String sub(String str,int len){ int j=0;  //标记字符串中汉字的个数byte[] b1 = str.getBytes();for(int i = 0;i<str.length();){char c = str.charAt(i);if(String.valueOf(c).getBytes().length==2){i+=2;j++;}else{i++;}if(i<len){continue;}else {return new String(b1, 0, len-j+1);}}return null;}}