testfiledescriptor.java

本书是一本为Java学习者在基础内容学习结束后进行课程设计时提供参考的指导书

package apibook.c3.s5;

import java.io.*;

//测试FileDescriptor类
public class TestFileDescriptor {
  public TestFileDescriptor() {
  }
  public static void main(String[] args) {
    FileOutputStream stdout =
        new FileOutputStream(FileDescriptor.out);
    FileInputStream stdin =
        new FileInputStream(FileDescriptor.in);
    try {
      StringBuffer sb = new StringBuffer();
      int c;//从标准输入读
      System.out.println("please input data(blank line to end):");
      while ((c=stdin.read()) > -1) {
          if (c == '\n' || c == '\r')
              break;
          sb.append((char)c);
      }

      //输出到标准输出
      byte[] buf = sb.toString().getBytes();
      stdout.write(buf);
      stdout.write('\n');
      stdout.flush();

      //测试valid函数
      String filename = "TestFileDescriptor.txt";
      FileInputStream in = new FileInputStream(filename);
      if (in.getFD().valid())//判断是否有效
        System.out.println("got valid file descriptor");
      else
        System.out.println("got invalid file descriptor");
      in.close();//关闭文件

      FileOutputStream out = new FileOutputStream(filename);
      String teststr = "this is a test from TestFileDescriptor";
      buf = teststr.getBytes();
      out.write(buf, 0, buf.length);//写入测试数据
      out.flush();               //刷新数据
      out.getFD().sync();        //将数据变化写到硬盘
      out.close();//关闭输出文件

    } catch (IOException e) {
        e.printStackTrace();
    }
  }

}