Permission denied error in Java for chmod command

I'd guess that chmod is a shell command, not an executable. Try running chmod through your shell. See more details here: Want to invoke a linux shell command from Java

I just had the same problem in my code. i solved this by add waitFor after exec. The "chmod" process is not finished when next command is executed. the code may look like:

p = Runtime.getRuntime.exec("chmod 777 xxx");
p.waitFor();
Runtime.getRuntime.exec("./xxx");

Yes, there is a difference. When you run the command from the terminal, it is you who is performing the action, and thus it is performed using your credentials. The Java application is running the command using the Java application's permissions. This is to prevent an application from running and then making dangerous, unwanted changes to the file system. Perhaps someone else can elaborate and give guidance to a workaround for this.