Java I/O的典型使用形式

 

//: c11:IOStreamDemo.java// Typical I/O stream configurations.// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002// www.BruceEckel.com. See copyright notice in CopyRight.txt.import java.io.*;public class IOStreamDemo {   // Throw exceptions to console:  public static void main(String[] args)   throws IOException {    // 1. Reading input by lines:    BufferedReader in =      new BufferedReader(        new FileReader("IOStreamDemo.java"));    String s, s2 = new String();    while((s = in.readLine())!= null)      s2 += s + "\n";    in.close();    // 1b. Reading standard input:    BufferedReader stdin =      new BufferedReader(        new InputStreamReader(System.in));          System.out.print("Enter a line:");    System.out.println(stdin.readLine());    // 2. Input from memory    StringReader in2 = new StringReader(s2);    int c;    while((c = in2.read()) != -1)      System.out.print((char)c);    // 3. Formatted memory input    try {      DataInputStream in3 =        new DataInputStream(          new ByteArrayInputStream(s2.getBytes()));      while(true)        System.out.print((char)in3.readByte());    } catch(EOFException e) {      System.err.println("End of stream");    }    // 4. File output    try {      BufferedReader in4 =        new BufferedReader(          new StringReader(s2));      PrintWriter out1 =        new PrintWriter(          new BufferedWriter(            new FileWriter("IODemo.out")));      int lineCount = 1;      while((s = in4.readLine()) != null )        out1.println(lineCount++ + ": " + s);      out1.close();    } catch(EOFException e) {      System.err.println("End of stream");    }    // 5. Storing & recovering data    try {      DataOutputStream out2 =        new DataOutputStream(          new BufferedOutputStream(            new FileOutputStream("Data.txt")));      out2.writeDouble(3.14159);      out2.writeUTF("That was pi");      out2.writeDouble(1.41413);      out2.writeUTF("Square root of 2");      out2.close();      DataInputStream in5 =        new DataInputStream(          new BufferedInputStream(            new FileInputStream("Data.txt")));      // Must use DataInputStream for data:      System.out.println(in5.readDouble());      // Only readUTF() will recover the       // Java-UTF String properly:      System.out.println(in5.readUTF());      // Read the following double and String:      System.out.println(in5.readDouble());      System.out.println(in5.readUTF());    } catch(EOFException e) {      System.err.println("End of stream");    }    // 6. Reading/writing random access files    RandomAccessFile rf =      new RandomAccessFile("rtest.dat", "rw");    for(int i = 0; i < 10; i++)      rf.writeDouble(i*1.414);    rf.close();    rf =      new RandomAccessFile("rtest.dat", "rw");    rf.seek(5*8);    rf.writeDouble(47.0001);    rf.close();    rf =      new RandomAccessFile("rtest.dat", "r");    for(int i = 0; i < 10; i++)      System.out.println(        "Value " + i + ": " +        rf.readDouble());    rf.close();   }} ///:~