从Java代码获取cmd命令的输出

Question

我有一个程序，可以从我的代码成功执行cmd命令，但我希望能够从cmd命令获取输出。我怎样才能做到这一点？

到目前为止，我的代码是：

Second.java：

public class Second {
    public static void main(String[] args) {
        System.out.println("Hello world from Second.java");
    }
}

和Main.java

public class Main {
    public static void main(String[] args) {
        String filename = args[1].substring(0, args[1].length() - 5);
        String cmd1 = "javac " + args[1];
        String cmd2 = "java " + filename;

        Runtime r = Runtime.getRuntime();
        Process p = r.exec(cmd1); // i can verify this by being able to see Second.class and running it successfully
        p = r.exec(cmd2); // i need to see this output to see if

        System.out.println("Done");
    }
}

我可以通过检查Second.class来检查第一个命令是否正常工作，但是如果该类产生了一些错误，我将如何看到该错误呢？

Answer 1

您需要流程的OutputStream（InputStream）（并且应该使用ProcessBuilder）…就像这样

public static void main(String[] args) {
  String filename = args[1].substring(0, args[1].length() - 5);
  String cmd1 = "javac " + args[1];
  String cmd2 = "java " + filename;

  try {
    // Use a ProcessBuilder
    ProcessBuilder pb = new ProcessBuilder(cmd1);

    Process p = pb.start();
    InputStream is = p.getInputStream();
    BufferedReader br = new BufferedReader(new InputStreamReader(is));
    String line = null;
    while ((line = br.readLine()) != null) {
      System.out.println(line);
    }
    int r = p.waitFor(); // Let the process finish.
    if (r == 0) { // No error
       // run cmd2.
    }
  } catch (Exception e) {
    e.printStackTrace();
  }
}