running java main class using subprocess.Popen in python

Question

I want to execute java main class main.java by python using subprocess.Popen(). main.java takes 3 args.

I wonder how to do it? For example I have a HelloWorld.java class:

public class HelloWorld {
 public static void main(String[] args) {
 System.out.println("Hello World!" + args[0]);
 } }

I tried to call it in python using the command:

print (subprocess.Popen('java C:/Users/testing/Hello.Main sayHello', shell=True, stdout=subprocess.PIPE).stdout.read())

where 'sayHello' is the string args I want to pass in. It said

Error: Could not find or load main class C:.Users.testing.Hello.Main

Thanks

Answer 1

You may run your java file with extension .class the following way:

java your.path.Main arg1 arg2

where,

• java - command, which runs the Java interpreter
• your.path.Main - full name of your class (without .class)
• arg1 arg2 - the arguments (written by spaces or between ")

Further, when you formatted this line, it transmits in subprocess.Popen() as argument.

subprocess.Popen('java your.path.Main arg1 arg2')

I'm not Python programmer, because I advice you to read documentation about this method.

• jfs: note: it won't work on POSIX systems; use a list argument instead: 'java your.path.Main arg1 arg2'.split()
• RLe: I tried it with simple helloworld class using: print (subprocess.Popen('java C:/Users/Testing/src/HelloWorld.Main', shell=True, stdout=subprocess.PIPE).stdout.read()) and got the error: Error: Could not find or load main class C:.Users.src.Hello
• RLe: @AndrewTobilko I did make HelloWorld.class and got that error which is why I don't get the reason :) and thanks for such a fast response
• RLe: @AndrewTobilko it works perfectly on command prompt when I was in the correct directory, but doesn't work when I typed in entire path such as java C:/Users/testing/HelloWorld it will return same error: Error: Could not find or load main class C:.Users.testing.HelloWorld it may be the problem since in python, I also put in full path like that
• Andrew: Let us continue this discussion in chat.