java io 例子

   public class TestIO{
    public static void main(String[] args) throws IOException{
    //1.以行为单位从一个文件读取数据
    BufferedReader in = new BufferedReader( new FileReader("F:\\nepalon\\TestIO.java"));
    String s, s2 = new String();
    while((s = in.readLine()) != null)
    s2 += s + "\n"; in.close();
    //1b. 接收键盘的输入
    BufferedReader stdin = new BufferedReader( new InputStreamReader(System.in));
    System.out.println("Enter a line:");
    System.out.println(stdin.readLine());
    //2. 从一个String对象中读取数据
    StringReader in2 = new StringReader(s2);
    int c;
    while((c = in2.read()) != -1)
    System.out.println((char)c);
    in2.close();
    //3. 从内存取出格式化输入
    try{ DataInputStream in3 = new DataInputStream( new ByteArrayInputStream(s2.getBytes()));
    while(true)
    System.out.println((char)in3.readByte());
    } catch(EOFException e){
    System.out.println("End of stream"); }
    //4. 输出到文件
    try{ BufferedReader in4 = new BufferedReader( new StringReader(s2));
    PrintWriter out1 = new PrintWriter( new BufferedWriter( new FileWriter("F:\\nepalon\\ TestIO.out")));
    int lineCount = 1; while((s = in4.readLine()) != null) out1.println(lineCount++ + "：" + s);
    out1.close(); in4.close();
    } catch(EOFException ex){
    System.out.println("End of stream"); }
    //5. 数据的存储和恢复
    try{ DataOutputStream out2 = new DataOutputStream( new BufferedOutputStream( new FileOutputStream("F:\\nepalon\\ Data.txt")));
    out2.writeDouble(3.1415926);
    out2.writeChars("\nThas was pi:writeChars\n");
    out2.writeBytes("Thas was pi:writeByte\n");
    out2.close();
    DataInputStream in5 = new DataInputStream( new BufferedInputStream( new FileInputStream("F:\\nepalon\\ Data.txt")));
    BufferedReader in5br = new BufferedReader( new InputStreamReader(in5));
    System.out.println(in5.readDouble()); System.out.println(in5br.readLine());
    System.out.println(in5br.readLine()); } catch(EOFException e){ System.out.println("End of stream");
    }
    //6. 通过RandomAccessFile操作文件
    RandomAccessFile rf = new RandomAccessFile("F:\\nepalon\\ rtest.dat", "rw");
    for(int i=0; i<10; i++)
    rf.writeDouble(i*1.414);
    rf.close();
    rf = new RandomAccessFile("F:\\nepalon\\ rtest.dat", "r");
    for(int i=0; i<10; i++)
    System.out.println("Value " + i + "：" + rf.readDouble());
    rf.close();
    rf = new RandomAccessFile("F:\\nepalon\\ rtest.dat", "rw");
    rf.seek(5*8);
    rf.writeDouble(47.0001); rf.close();
    rf = new RandomAccessFile("F:\\nepalon\\ rtest.dat", "r"); for(int i=0; i<10; i++)
    System.out.println("Value " + i + "：" + rf.readDouble()); rf.close(); } }