Set an umask before launching Process with JAVA

Question

I would add a umask before launching process with java, but the java process api (i use java 9) does not provide a method to set an umask.

I tried to run a process by executing umask with a value that allows me to create but not read (0644). it did not work ...

Optional<String> umask = ProcessUtil.getUmask();
if (!umask.isPresent()) {
    this.restartOnFail();
    return;
}
ProcessUtil.setUmask(parent.config.umask);
this.timeAtLaunch = System.currentTimeMillis();
this.status = ProcessStatus.LAUNCHING;
this.process = pb.start();
this.onExitProcess();
ProcessUtil.setUmask(umask.get());

The setUmask code is :

public static void setUmask(String mask) {
    try {
        String[] commands = {"umask", mask};
        Process exec = Runtime.getRuntime().exec(commands);
        exec.waitFor();
    } catch (Exception e) {
        Server.global.logErr("Impossible to set umask for %s.", mask);
    }
}

I have tried to do that and it seems to not work (I launched a process that creates a file and reads it, and it should just create it and make a error when reading it.) because the process created a file that did not have the permissions set by umask. He was able to read the file, which should not have happened ...

I have created a ready runnable class :

import java.io.*;

public class StackOverFlowTest {

    public static void setUmask(String mask) {
        try {
            String[] commands = {"umask", mask};
            Process exec = Runtime.getRuntime().exec(commands);
            exec.waitFor();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void runCommand(String [] command) throws IOException, InterruptedException {
        Runtime rt = Runtime.getRuntime();
        Process proc = rt.exec(command);
        BufferedReader stdInput = new BufferedReader(new InputStreamReader(proc.getInputStream()));
        BufferedReader stdError = new BufferedReader(new InputStreamReader(proc.getErrorStream()));
        String s = null;
        while ((s = stdInput.readLine()) != null) {
            System.out.println("stdout: " + s);
        }
        while ((s = stdError.readLine()) != null) {
            System.out.println("stderr: " + s);
        }
        proc.waitFor();
    }

    public static void main(String[] args) {
        setUmask("0644"); // set this permission -----w--w-

        String[] create = {"touch", "file.stackoverflow"};
        String[] read = {"cat", "file.stackoverflow"};

        try {
            runCommand(create);
            runCommand(read);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

This code actually don't show any error when cat is launch and it's a problem !

(Sorry for my english)

So there is someone that have a tip to launch process with some permissions with java ?