在Java 中FileReader与FileWriter有哪些区别

  package java.io;
 public class FileReader extends InputStreamReader {
   public FileReader(String fileName) throws FileNotFoundException {
     super(new FileInputStream(fil java io系列21之 InputStreamReader和OutputStreamWritereName));
   }
   public FileReader(File file) throws FileNotFoundException {
     super(new FileInputStream(file));
   }
   public FileReader(FileDescriptor fd) {
     super(new FileInputStream(fd));
   }
 }

 package java.io;
 public class FileWriter extends OutputStreamWriter {
   public FileWriter(String fileName) throws IOException {
     super(new FileOutputStream(fileName));
   }
   public FileWriter(String fileName, boolean append) throws IOException {
     super(new FileOutputStream(fileName, append));
   }
   public FileWriter(File file) throws IOException {
     super(new FileOutputStream(file));
   }
   public FileWriter(File file, boolean append) throws IOException {
     super(new FileOutputStream(file, append));
   }
   public FileWriter(FileDescriptor fd) {
     super(new FileOutputStream(fd));
   }
 } 

import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.FileWriter;;
 import java.io.FileReader;
 import java.io.IOException;
 /**
  * FileReader 和 FileWriter 测试程序
 *
 * 
 */
 public class FileReaderWriterTest {
   private static final String FileName = "file.txt";
   private static final String CharsetName = "utf-8";
   public static void main(String[] args) {
     testWrite();
     testRead();
   }
   /**
   * OutputStreamWriter 演示函数
   *
   */
   private static void testWrite() {
     try {
       // 创建文件“file.txt”对应File对象
       File file = new File(FileName);
       // 创建FileOutputStream对应FileWriter：将字节流转换为字符流，即写入out的数据会自动由字节转换为字符。
       FileWriter out = new FileWriter(file);
      // 写入10个汉字
       out1.write("字节流转为字符流示例");
      // 向“文件中”写入"0123456789"+换行符
      out1.write("0123456789\n");
      out1.close();
     } catch(IOException e) {
       e.printStackTrace();
     }
   }
   /**
   * InputStreamReader 演示程序
   */
   private static void testRead() {
     try {
      // 方法1：新建FileInputStream对象
       // 新建文件“file.txt”对应File对象
       File file = new File(FileName);
       FileReader in1 = new FileReader(file);
       // 测试read()，从中读取一个字符
      char c1 = (char)in1.read();
       System.out.println("c1="+c1);
       // 测试skip(long byteCount)，跳过4个字符
       in1.skip(6);
       // 测试read(char[] cbuf, int off, int len)
       char[] buf = new char[10];
       in1.read(buf, 0, buf.length);
       System.out.println("buf="+(new String(buf)));
       in.close();
     } catch(IOException e) {
       e.printStackTrace();
     }
   }
 }