Java中的freopen()

 C++中有freopen()函数用来从文件汇中输入测试数组，Java用下面的方式达到这个目的

public class Main {
  static private final String INPUT = "C:/input.txt";
  static private final String OUTPUT = "C:/output.txt";
 
  public static void main(String args[]) {
      // open I/O files
      FileInputStream instream = null;
      PrintStream outstream = null;
   
      try {
          instream = new FileInputStream(INPUT);
          outstream = new PrintStream(new FileOutputStream(OUTPUT));
          System.setIn(instream);
          System.setOut(outstream);
      } catch (Exception e) {
          System.err.println("Error Occurred.");
      }
   
      Scanner in = new Scanner(System.in);
      for (;in.hasNext();) {
          int x = in.nextInt();
          System.out.println(x);
      }
   
      System.err.println("done.");
      return;
  }
 
}

 转债自：https://www.cnblogs.com/duanguyuan/p/3365843.html

或者下面中方式：

public static void main(String[] args) throws Exception {
        // 输入重定向
        BufferedInputStream in = new BufferedInputStream(new FileInputStream("std.in"));
        System.setIn(in);
        Scanner stdin = new Scanner(System.in);
        int a = stdin.nextInt();
        int b = stdin.nextInt();
        // 输出重定向
        PrintStream out = new PrintStream(new FileOutputStream("estdout.pc2"));
        System.setOut(out);
        System.out.print(a + b);
        out.close(); // 关闭重定向
    }

转载自：https://blog.csdn.net/fightforyourdream/article/details/17329671