通过另一个Java程序运行具有输入语句的Java程序

Question

I am trying to develop an online Java IDE. I am not able to get input from another java program.

The second program: HelloWorld.java

class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello world..................");
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter Name");
        String name = sc.nextLine();
        System.out.println("you entered " + name);
        sc.close();
    }
}

public class Demo {
    public static void main(String[] args) {
        Process pro = Runtime.getRuntime().exec(javac HelloWorld.java);
        Process pro1 = Runtime.getRuntime().exec(java HelloWorld);
    }
}

The problem is that when I compile and run the above program I am getting "Enter Name" of System.out.println("Enter Name"); in HelloWorld.java . However, after that nothing happens.

Answer 1

It is not the same "Runtime". Calling exec starts a new process. Interaction with a running process should use the input and output stream from executing the process. eg use the following:

Process p = Runtime.getRuntime().exec(*******);
InputStream is = p.getInputStream();
InputStream es = p.getErrorStream();
OutputStream os = p.getOutputStream(); 

start with a simple example of passing param to the process manually and afterwards see how you can connect streams from different processes