java 获取字符串编码类型

public static String getEncoding(String str) {      
       String encode = "GB2312";      
      try {      
          if (str.equals(new String(str.getBytes(encode), encode))) {      
               String s = encode;      
              return s;      
           }      
       } catch (Exception exception) {      
       }      
       encode = "ISO-8859-1";      
      try {      
          if (str.equals(new String(str.getBytes(encode), encode))) {      
               String s1 = encode;      
              return s1;      
           }      
       } catch (Exception exception1) {      
       }      
       encode = "UTF-8";      
      try {      
          if (str.equals(new String(str.getBytes(encode), encode))) {      
               String s2 = encode;      
              return s2;      
           }      
       } catch (Exception exception2) {      
       }      
       encode = "GBK";      
      try {      
          if (str.equals(new String(str.getBytes(encode), encode))) {      
               String s3 = encode;      
              return s3;      
           }      
       } catch (Exception exception3) {      
       }      
      return "";      
   }