幾種常用輸出輸出流的使用

2019-11-18 14:42:21

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// : c12:IOStreamDemo.java
// Typical I/O stream configurations.
// {RunByHand}
// {Clean: IODemo.out,Data.txt,rtest.dat}
// From 'Thinking in Java, 3rd ed.' (c) BrUCe Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PRintWriter;
import java.io.Random accessFile;
import java.io.StringReader;

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) {
      throw new RuntimeException(e);
    }

    // 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();
  }
} ///:~

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