Java按字节截取字符串(GBK编码、UTF-8编码实现)

 package FileDemo;

 import java.io.IOException;

 public class CutStringTest {

     /**
      * @param args
      * @throws IOException
      */
     public static void main(String[] args) throws IOException {

         String str = "ab你好cd谢谢";
         /*byte buf[]=str.getBytes("GBK");
         for(byte ch:buf){
             System.out.println(Integer.toBinaryString(ch));
         }*/
         int len = str.getBytes("gbk").length;
         for (int x = 0; x < len; x++) {
             System.out.println("截取" + (x + 1) + "字节结果时："
                     + cutStringByByte(str, x + 1));
         }
         String str1 = "ab你好cd杮";
         int len1 = str.getBytes("gbk").length;
         for (int x = 0; x < len1; x++) {
             System.out.println("截取" + (x + 1) + "字节结果时："
                     + cutStringByU8(str1, x + 1));
         }
     }

     // 使用UTF-8编码表进行截取字符串，一个汉字对应三个负数，一个英文字符对应一个正数
     private static String cutStringByU8(String str, int len) throws IOException {

         byte[] buf = str.getBytes("utf-8");
         int count = 0;
         for (int x = len - 1; x >= 0; x--) {
             if (buf[x] < 0) {
                 count++;
             } else {
                 break;
             }
         }
         if (count % 3 == 0) {
             return new String(buf, 0, len, "utf-8");
         } else if (count % 3 == 1) {
             return new String(buf, 0, len - 1, "utf-8");
         } else {
             return new String(buf, 0, len - 2, "utf-8");
         }
     }

     // 使用GBK编码表进行字符串的截取，一个英文字符对应码表一个正数，一个汉字对应两个负数
     public static String cutStringByByte(String str, int len)
             throws IOException {
         byte[] buf = str.getBytes("gbk");
         int count = 0;
         for (int x = len - 1; x >= 0; x--) {
             if (buf[x] < 0) {
                 count++;
             } else {
                 break;
             }
         }
         if (count % 2 == 0) {
             return new String(buf, 0, len, "gbk");
         } else {
             return new String(buf, 0, len - 1, "gbk");
         }
     }

 }