Character Set and Encoding

Part:   1  2   3  4 

(Continued from previous part...)

Methods to Encode Characters

There are 4 methods to encode characters:

• CharsetEncoder.encode()
• Charset.encode()
• String.getBytes()
• OutputStreamWriter.write()

Here is a program that demonstrate how to encode characters in each of the above 4 methods:

/**
 * EncodingSampler.java
 * Copyright (c) 2002 by Dr. Herong Yang
 */
import java.io.*;
import java.nio.*;
import java.nio.charset.*;
class EncodingSampler {
   static String dfltCharset = null;
   static char[] chars={0x0000, 0x003F, 0x0040, 0x007F, 0x0080, 0x00BF,
                        0x00C0, 0x00FF, 0x0100, 0x3FFF, 0x4000, 0x7FFF,
                        0x8000, 0xBFFF, 0xC000, 0xEFFF, 0xF000, 0xFFFF};
   static char hexDigit[] = {'0', '1', '2', '3', '4', '5', '6', '7',
                             '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
   public static void main(String[] arg) {
      String charset = null;
      if (arg.length>0) charset = arg[0];
      OutputStreamWriter o = new OutputStreamWriter(
         new ByteArrayOutputStream());
      dfltCharset = o.getEncoding();
      if (charset==null) System.out.println("Default ("+dfltCharset
         +") encoding:");
      else System.out.println(charset+" encoding:");
      System.out.println("Char, String, Writer, Charset, Encoder");
      for (int i=0; i<chars.length; i++) {
         char c = chars[i];
         byte[] b1 = encodeByString(c,charset);
         byte[] b2 = encodeByWriter(c,charset);
         byte[] b3 = encodeByCharset(c,charset);
         byte[] b4 = encodeByEncoder(c,charset);
         System.out.print(charToHex(c)+",");
         printBytes(b1);
         System.out.print(",");
         printBytes(b2);
         System.out.print(",");
         printBytes(b3);
         System.out.print(",");
         printBytes(b4);
         System.out.println("");
      }
   }
   public static byte[] encodeByCharset(char c, String cs) {
      Charset cso = null;
      byte[] b = null;
      try {   	
         if (cs==null) cso = Charset.forName(dfltCharset);
         else cso = Charset.forName(cs);
         ByteBuffer bb = cso.encode(String.valueOf(c));
         b = copyBytes(bb.array(),bb.limit());
      } catch (IllegalCharsetNameException e) {
         System.out.println(e.toString());
      }      	
      return b;
   }
   public static byte[] encodeByEncoder(char c, String cs) {
      Charset cso = null;
      byte[] b = null;
      try {   	
         if (cs==null) cso = Charset.forName(dfltCharset);
         else cso = Charset.forName(cs);
         CharsetEncoder e =  cso.newEncoder();
         e.reset();
         ByteBuffer bb = e.encode(CharBuffer.wrap(new char[] {c}));
         b = copyBytes(bb.array(),bb.limit());
      } catch (IllegalCharsetNameException e) {
         System.out.println(e.toString());
      } catch (CharacterCodingException e) {
         //System.out.println(e.toString());
         b = new byte[] {(byte)0x00};
      }      	
      return b;
   }
   public static byte[] encodeByString(char c, String cs) {
      String s = String.valueOf(c);
      byte[] b = null;
      if (cs==null) {
         b = s.getBytes();
      } else {
         try {
            b = s.getBytes(cs);
         } catch (UnsupportedEncodingException e) {
            System.out.println(e.toString());
         }
      }
      return b;
   }
   public static byte[] encodeByWriter(char c, String cs) {
      byte[] b = null;
      ByteArrayOutputStream bs = new ByteArrayOutputStream();
      OutputStreamWriter o = null;
      if (cs==null) {
         o = new OutputStreamWriter(bs);
      } else {
         try {
            o = new OutputStreamWriter(bs, cs);
         } catch (UnsupportedEncodingException e) {
            System.out.println(e.toString());
         }
      }
      String s = String.valueOf(c);
      try {
         o.write(s);
         o.flush();
         b = bs.toByteArray();
         o.close();
      } catch (IOException e) {
         System.out.println(e.toString());
      }
      return b;
   }
   public static byte[] copyBytes(byte[] a, int l) {
      byte[] b = new byte[l];
      for (int i=0; i<Math.min(l,a.length); i++) b[i] = a[i];
      return b;
   }
   public static void printBytes(byte[] b) {
      for (int j=0; j<b.length; j++)
         System.out.print(" "+byteToHex(b[j]));
   }
   public static String byteToHex(byte b) {
      char[] a = { hexDigit[(b >> 4) & 0x0f], hexDigit[b & 0x0f] };
      return new String(a);
   }
   public static String charToHex(char c) {
      byte hi = (byte) (c >>> 8);
      byte lo = (byte) (c & 0xff);
      return byteToHex(hi) + byteToHex(lo);
   }
}

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Part:   1  2   3  4