public class KeyinTest {
      public static void main(String[] args) {
        try (InputStreamReader reader = new InputStreamReader(System.in);
                  //BufferedReader has readLine() to read by Line
            BufferedReader br = new BufferedReader(reader)) {
          String line = null;
          while ((line = br.readLine()) != null) {
            if (line.equals("exit")) {
              System.exit(1);
            }
            ;
            System.out.println("输出的内容是:" + line);
          }
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }

    public class PushbackTest {
      public static void main(String[] args) {
        // 指定推回缓冲区长度为64.
        try (PushbackReader pr = new PushbackReader(new FileReader(
            "src/inputandoutput/PushbackTest.java"), 64)) {
          char[] buff = new char[32];
          String lastContent = "";
          int hasRead = 0;
          while ((hasRead = pr.read(buff)) > 0) {
            String content = new String(buff, 0, hasRead);
            int targetIndex = 0;
            if ((targetIndex = (content + lastContent)
                .indexOf("new PushbackIndex")) > 0) {
              pr.unread((lastContent + content).toCharArray());
              if (targetIndex > 32) {
                buff = new char[targetIndex];
              }
              pr.read(buff, 0, targetIndex);
              System.out.print(new String(buff, 0, targetIndex));
              System.exit(0);
            } else {
              System.out.println(lastContent);
              lastContent = content;
            }
          }
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }

public class RedirectOut {
  public static void main(String[] args) {
    try (PrintStream ps = new PrintStream(new FileOutputStream("out.txt"))) {
      // redirect the output to ps
      System.setOut(ps);
      System.out.println("hello");
      System.out.println(new RedirectOut());
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}

    public class RedirectIn {
      public static void main(String[] args) {
        try (FileInputStream in = new FileInputStream(
            "src/inputandoutput/RedirectIn.java")) {
          System.setIn(in);
          Scanner scan = new Scanner(System.in);
          // only use \n as Delimiter
          scan.useDelimiter("\n");
          while (scan.hasNext()) {
            System.out.println("content:" + scan.next());
          }
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }

    public class ReadFromTest {
      public static void main(String[] args) throws IOException {
        Process p = Runtime.getRuntime().exec("javac");
        try (BufferedReader br = new BufferedReader(new InputStreamReader(
            p.getErrorStream()))) {
          String buff = null;
          while ((buff = br.readLine()) != null) {
            System.out.println(buff);
          }
        }
      }
    }

    public class WriteToProcess {
      public static void main(String[] args) throws IOException {
        Process p = Runtime.getRuntime().exec("java ReadStandard");
        try (
        // 以p进程的输出流创建PrintStream，该输出流对本进程为输出流，对p进程则为输入流
        PrintStream ps = new PrintStream(p.getOutputStream())) {
          ps.println("normal string");
          ps.println(new WriteToProcess());
        }
      }
    }
    class ReadStandard {
      public static void main(String[] args) throws FileNotFoundException {
        try (Scanner scan = new Scanner(System.in);
            PrintStream ps = new PrintStream(
                new FileOutputStream("out.txt"))) {
          scan.useDelimiter("\n");
          while (scan.hasNext()) {
            ps.println("KeyBoards input:" + scan.next());
          }
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }