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

 1 public class Main {
 2   static private final String INPUT = "C:/input.txt";
 3   static private final String OUTPUT = "C:/output.txt";
 4  
 5   public static void main(String args[]) {
 6       // open I/O files
 7       FileInputStream instream = null;
 8       PrintStream outstream = null;
 9    
10       try {
11           instream = new FileInputStream(INPUT);
12           outstream = new PrintStream(new FileOutputStream(OUTPUT));
13           System.setIn(instream);
14           System.setOut(outstream);
15       } catch (Exception e) {
16           System.err.println("Error Occurred.");
17       }
18    
19       Scanner in = new Scanner(System.in);
20       for (;in.hasNext();) {
21           int x = in.nextInt();
22           System.out.println(x);
23       }
24    
25       System.err.println("done.");
26       return;
27   }
28  
29 }

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

或者下面中方式：

 1 public static void main(String[] args) throws Exception {
 2         // 输入重定向
 3         BufferedInputStream in = new BufferedInputStream(new FileInputStream("std.in"));
 4         System.setIn(in);
 5         Scanner stdin = new Scanner(System.in);
 6         int a = stdin.nextInt();
 7         int b = stdin.nextInt();
 8         // 输出重定向
 9         PrintStream out = new PrintStream(new FileOutputStream("estdout.pc2"));
10         System.setOut(out);
11         System.out.print(a + b);
12         out.close(); // 关闭重定向
13     }

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

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