java 字符串截取的实例详解

import java.io.UnsupportedEncodingException;import org.junit.Test;/** * @author<a href="mailto:953801304@qq.com" rel="external nofollow" >胡龙华</a> * @version 2017-4-4 下午1:08:45 * @fileName StringCut.java */public class StringCut {  @Test  public void analyze(){    String str1 = "你好abc";    byte[] bs1=null;    byte[] bs2=null;    try {       bs1 = str1.getBytes("GBK");       System.out.println("---GBK---");       for(byte b:bs1){         System.out.print(b+" ");       }       System.out.println();      //-60 -29 -70 -61 97 98 99       // 发现规律，再gbk中一个中文汉字 都是以两个字节 小于0的数存储       bs2 = str1.getBytes("utf-8");       System.out.println("---utf-8---");       for(byte b:bs2){         System.out.print(b+" ");       }      //-28 -67 -96 -27 -91 -67 97 98 99       // 发现规律，在utf-8中一个中文汉字 是以三个字节 小于0 的数存储    } catch (UnsupportedEncodingException e) {      e.printStackTrace();    }  }  /**   * 思路：从第len个往前数，连续2的倍数个负数则全部输出，单数个则去掉最后一个输出   * @param str   * @param len   * @return   */  private static String StringCutByGBK(String str,int len){    byte[] bs = null;    try {      int count = 0;      bs = str .getBytes("GBK");      for(int i=len-1;i>=0;i--){        if(bs[i]<0){          count++;        }else{          break;        }        // 0  1  2  3  4 5  6 7  8  9  10 11 12        }  //-60 -29 -70 -61 -80 -95 97 98 99 -76 -17 -72 -25       if(count%2==0){        String s=new String(bs, 0, len, "GBK");        System.out.println("截取"+len+"个字符："+s);      }else{        String s=new String(bs, 0, len-1, "GBK");        System.out.println("截取"+len+"个字符："+s);      }    } catch (UnsupportedEncodingException e) {      e.printStackTrace();    }    return null;  }  /**   * 思路：从第len个往前数，连续3的倍数个负数则全部输出，其他情况则去掉最后count%3个输出   * @param str   * @param len   * @return   */  private static String StringCutByUTF8(String str,int len){    byte[] bs = null;    try {      int count = 0;      bs = str .getBytes("UTF-8");      for(int i=len-1;i>=0;i--){        if(bs[i]<0){          count++;        }else{          break;        }      }        // 0  1  2  3  4  5  6 7 8 9  10 11 12      //-60 -29 -70 -61 -80 -95 97 98 99 -76 -17 -72 -25       if(count%3==0){        String s=new String(bs, 0, len, "UTF-8");        System.out.println("截取"+len+"个字符："+s);      }else{        String s=new String(bs, 0, len-count%3, "UTF-8");        System.out.println("截取"+len+"个字符："+s);      }    } catch (UnsupportedEncodingException e) {      e.printStackTrace();    }    return null;  }  @Test  public void TEST() {    String str = "你好啊abc达哥";    try {      System.out.println("---测试gbk---");      byte bs [] = str.getBytes("GBK");      for(int i=0;i<=bs.length;i++){        //System.out.print(bs[i]+" ");        StringCutByGBK(str,i);      }      System.out.println("---测试UTF-8---");      byte bs2 [] = str.getBytes("utf-8");      for(int i=0;i<=bs2.length;i++){        //System.out.print(bs[i]+" ");        StringCutByUTF8(str,i);      }    } catch (UnsupportedEncodingException e) {      // TODO Auto-generated catch block      e.printStackTrace();    }  }}