Java字符集编码与转码
 
Java字符的class代码总是Unicode字符集的UTF-16编码,运行时内存中的字符串在没有指定编码的时候也总是Unicode编码。
 
Java编译时候,会将java文件的编码按照指定编码或者(系统默认的)编码转换为Unicode并加载到内存中进行编译。
 
下面给出一个Java转码工具,没有测试过,呵呵:
 
package lavasoft.common;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.io.*;

/**
* 转码工具,全面支持文件、字符串的转码
*
* @author Administrator 2009-11-29 16:14:21
*/

public class EncodingToolkit {
        private static Log log = LogFactory.getLog(EncodingToolkit.class);

        public static void main(String[] args) {
                String han = "汉";


                System.out.println("---------");
        }

        /**
         * 对字符串重新编码
         *
         * @param text                字符串
         * @param resEncoding 源编码
         * @param newEncoding 新编码
         * @return 重新编码后的字符串
         */

        public static String reEncoding(String text, String resEncoding, String newEncoding) {
                String rs = null;
                try {
                        rs = new String(text.getBytes(resEncoding), newEncoding);
                } catch (UnsupportedEncodingException e) {
                        log.error("读取文件为一个内存字符串失败,失败原因是使用了不支持的字符编码");
                        throw new RuntimeException(e);
                }
                return rs;
        }

        /**
         * 重新编码Unicode字符串
         *
         * @param text                源字符串
         * @param newEncoding 新的编码
         * @return 指定编码的字符串
         */

        public static String reEncoding(String text, String newEncoding) {
                String rs = null;
                try {
                        rs = new String(text.getBytes(), newEncoding);
                } catch (UnsupportedEncodingException e) {
                        log.error("读取文件为一个内存字符串失败,失败原因是使用了不支持的字符编码" + newEncoding);
                        throw new RuntimeException(e);
                }
                return rs;
        }

        /**
         * 文本文件重新编码
         *
         * @param resFile         源文件
         * @param resEncoding 源文件编码
         * @param distFile        目标文件
         * @param newEncoding 目标文件编码
         * @return 转码成功时候返回ture,否则false
         */

        public static boolean reEncoding(File resFile, String resEncoding, File distFile, String newEncoding) {
                boolean flag = true;
                InputStreamReader reader = null;
                OutputStreamWriter writer = null;
                try {
                        reader = new InputStreamReader(new FileInputStream(resFile), resEncoding);
                        writer = new OutputStreamWriter(new FileOutputStream(distFile), newEncoding);
                        char buf[] = new char[1024 * 64];         //字符缓冲区
                        int len;
                        while ((len = reader.read(buf)) != -1) {
                                writer.write(buf, 0, len);
                        }
                        writer.flush();
                        writer.close();
                        reader.close();
                } catch (FileNotFoundException e) {
                        flag = false;
                        log.error("没有找到文件,转码发生异常!");
                        throw new RuntimeException(e);
                } catch (IOException e) {
                        flag = false;
                        log.error("读取文件为一个内存字符串失败,失败原因是读取文件异常!");
                        throw new RuntimeException(e);
                } finally {
                        if (reader != null) try {
                                reader.close();
                        } catch (IOException e) {
                                flag = false;
                                throw new RuntimeException(e);
                        } finally {
                                if (writer != null) try {
                                        writer.close();
                                } catch (IOException e) {
                                        flag = false;
                                        throw new RuntimeException(e);
                                }
                        }
                }
                return flag;
        }

        /**
         * 读取文件为一个Unicode编码的内存字符串,保持文件原有的换行格式
         *
         * @param resFile    源文件对象
         * @param encoding 文件字符集编码
         * @return 文件内容的Unicode字符串
         */

        public static String file2String(File resFile, String encoding) {
                StringBuffer sb = new StringBuffer();
                try {
                        LineNumberReader reader = new LineNumberReader(new BufferedReader(new InputStreamReader(new FileInputStream(resFile), encoding)));
                        String line;
                        while ((line = reader.readLine()) != null) {
                                sb.append(line).append(System.getProperty("line.separator"));
                        }
                        reader.close();
                } catch (UnsupportedEncodingException e) {
                        log.error("读取文件为一个内存字符串失败,失败原因是使用了不支持的字符编码" + encoding);
                        throw new RuntimeException(e);
                } catch (FileNotFoundException e) {
                        log.error("读取文件为一个内存字符串失败,失败原因所给的文件" + resFile + "不存在!");
                        throw new RuntimeException(e);
                } catch (IOException e) {
                        log.error("读取文件为一个内存字符串失败,失败原因是读取文件异常!");
                        throw new RuntimeException(e);
                }
                return sb.toString();
        }

        /**
         * 使用指定编码读取输入流为一个内存Unicode字符串,保持文件原有的换行格式
         *
         * @param in             输入流
         * @param encoding 构建字符流时候使用的字符编码
         * @return Unicode字符串
         */

        public static String stream2String(InputStream in, String encoding) {
                StringBuffer sb = new StringBuffer();
                LineNumberReader reader = null;
                try {
                        reader = new LineNumberReader(new BufferedReader(new InputStreamReader(in, encoding)));
                        String line;
                        while ((line = reader.readLine()) != null) {
                                sb.append(line).append(System.getProperty("line.separator"));
                        }
                        reader.close();
                        in.close();
                } catch (UnsupportedEncodingException e) {
                        log.error("读取文件为一个内存字符串失败,失败原因是使用了不支持的字符编码" + encoding);
                        throw new RuntimeException(e);
                } catch (IOException e) {
                        log.error("读取文件为一个内存字符串失败,失败原因是读取文件异常!");
                        throw new RuntimeException(e);
                } finally {
                        if (in != null) try {
                                in.close();
                        } catch (IOException e) {
                                log.error("关闭输入流发生异常!", e);
                                throw new RuntimeException(e);
                        }
                }
                return sb.toString();
        }

        /**
         * 字符串保存为制定编码的文本文件
         *
         * @param text         字符串
         * @param distFile 目标文件
         * @param encoding 目标文件的编码
         * @return 转换成功时候返回ture,否则false
         */

        public static boolean string2TextFile(String text, File distFile, String encoding) {
                boolean flag = true;
                if (!distFile.getParentFile().exists()) distFile.getParentFile().mkdirs();
                OutputStreamWriter writer = null;
                try {
                        writer = new OutputStreamWriter(new FileOutputStream(distFile), encoding);
                        writer.write(text);
                        writer.close();
                } catch (IOException e) {
                        flag = false;
                        log.error("将字符串写入文件发生异常!");
                        throw new RuntimeException(e);
                } finally {
                        if (writer != null) try {
                                writer.close();
                        } catch (IOException e) {
                                log.error("关闭输出流发生异常!", e);
                                throw new RuntimeException(e);
                        }
                }
                return flag;
        }
}