Question

Im trying to compile some java files using the Runtime.getRuntime.exec(command) and im generating the command. The code below shows what i am doing:

String command = "javac ";
    for(String s: this.getPackages())
    {
        command = command + "/home/benuni/CompileFiles/" + project + "/" + s + "/*.java ";
    }

    try {
        System.out.println("command: '"+ command +"'");
        Process pro = Runtime.getRuntime().exec(command);
         printLines(" stderr:", pro.getErrorStream());

        pro.waitFor();

This is giving the following output:

command: 'javac /home/benuni/CompileFiles/HelloWorldProject/HelloWorldPackage/*.java '
stderr: javac: file not found:     /home/benuni/CompileFiles/HelloWorldProject/HelloWorldPackage/*.java
 stderr: Usage: javac <options> <source files>
 stderr: use -help for a list of possible options

and its not working.. but if i copy the command into my shell, it works no problem… any ideas?

Answer 1

Java doesn’t expand the * wildcard for you. That’s a facility of the shell. Instead, you’ll need to list the directory to get all of the contained files.

Something like this would do the trick to build up your command:

    File[] files = new File("/home/benuni/CompileFiles/" + project + "/" + s).listFiles(new FilenameFilter() {
        @Override
        public boolean accept(File dir, String name) {
            return name.endsWith(".java");
        }
    });

    StringBuilder command = new StringBuilder("javac");
    for(File file : files) {
        command.append(" ").append(file.getAbsolutePath());
    }