testprintwriters.java

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// TestPrintWriters.java
import java.io.*;

public class TestPrintWriters
{
  // Main method: args[0] is the output file
  public static void main(String[] args)
  {
    // 声明打印流
    PrintWriter pw = null;

    // 检查命令参数是否存在
    if (args.length != 1)
    {
      System.out.println("输入命令参数文件");
      System.exit(0);
    }

    File tempFile = new File(args[0]);

    if (tempFile.exists())
    {
      System.out.println("The file " + args[0] +
        " already exists, delete it, rerun the program");
      System.exit(0);
    }

    // 写数据
    try
    {
      
      pw = new PrintWriter(new FileOutputStream(tempFile), true);
      for (int i=0; i<10; i++)
        pw.print(" "+(int)(Math.random()*1000));
    }
    catch (IOException ex)
    {
      System.out.println(ex.getMessage());
    }
    finally
    {
      // 关闭文件
      if (pw != null) pw.close();
    }
  }
}