java初学者实践教程22－输入/输出

 //这是一个字节流的例子，以InputStream与OutputStream为基础类

import java.io.*;

class ByteArrayOutputStreamDemo {

    public static void main(String args[]) throws IOException {

    ByteArrayOutputStream f = new ByteArrayOutputStream();

    String s = "This should end up in the array";

    byte buf[] = s.getBytes();

    f.write(buf);

        System.out.println("Buffer as a string");

        System.out.println(f.toString());

        System.out.println("Into array");

    byte b[] = f.toByteArray();

    for (int i=0; i<b.length; i++) {

        System.out.print((char) b[i]);}

        System.out.println("\nTo an OutputStream()");

        //输出到文件test.txt中

        OutputStream f2 = new FileOutputStream("test.txt");

        f.writeTo(f2);

        f2.close();

        System.out.println("Doing a reset");

        f.reset();

    for (int i=0; i<3; i++)

    f.write('X');

        System.out.println(f.toString());}}

//字符流的例子，以Reader与Writer为基础类

import java.io.*;

public class CharArrayReaderDemo {

   public static void main(String args[]) throws IOException {

   String tmp = "abcdefghijklmnopqrstuvwxyz";

   int length = tmp.length();

   char c[] = new char[length];

   tmp.getChars(0, length, c, 0);

   CharArrayReader input1 = new CharArrayReader(c);

   CharArrayReader input2 = new CharArrayReader(c, 0, 5);

   int i;

       System.out.println("input1 is:");

   while((i = input1.read()) != -1) {

       System.out.print((char)i);}

       System.out.println();

       System.out.println("input2 is:");

   while((i = input2.read()) != -1) {

       System.out.print((char)i);}

       System.out.println();

   }}

//文件流的例子

import java.io.*;

class FileInputStreamDemo {

   public static void main(String args[]) throws Exception {

   int size;

   InputStream f =

   new FileInputStream("FileInputStreamDemo.java");

       System.out.println("Total Available Bytes: " +

       (size = f.available()));

   int n = size/40;

       System.out.println("First " + n +

       " bytes of the file one read() at a time");

   for (int i=0; i < n; i++) {

       System.out.print((char) f.read());

       }

       System.out.println("\nStill Available: " + f.available());

       System.out.println("Reading the next " + n +

       " with one read(b[])");

   byte b[] = new byte[n];

   if (f.read(b) != n) {

       System.err.println("couldn't read " + n + " bytes.");

       }

       System.out.println(new String(b, 0, n));

       System.out.println("\nStill Available: " + (size = f.available()));

       System.out.println("Skipping half of remaining bytes with skip()");

   f.skip(size/2);

       System.out.println("Still Available: " + f.available());

       System.out.println("Reading " + n/2 + " into the end of array");

   if (f.read(b, n/2, n/2) != n/2) {

       System.err.println("couldn't read " + n/2 + " bytes.");

       }

       System.out.println(new String(b, 0, b.length));

       System.out.println("\nStill Available: " + f.available());

   f.close();

   }

}