how to get the command line arguments from another class with java

Question

so suppose I have a java package....

it's got the main class with the main method

and then it's got a whole bunch of other classes.....

my question is, is it possible to get the args that was passed into the main method from these other classes that are not part of the main class but in the same package...

Solution 1

No, not portably, there may be some trickery based on the JVM implementation but I've never seen it, and it would be a very bad idea to rely on it even if it existed.

If you want those values elsewhere, the main function needs to make them available somehow.

---

An easy way to do this (not necessarily the best way) is to simply store away the strings as the first thing in main and provide a means for getting at them:

Scratch2.java:

public class Scratch2 {
    // Arguments and accessor for them.

    private static String[] savedArgs;
    public static String[] getArgs() {
        return savedArgs;
    }

    public static void main(String[] args) {
        // Save them away for later.

        savedArgs = args;

        // Test that other classes can get them.

        CmdLineArgs cla = new CmdLineArgs();
        cla.printArgs();
    }
}

CmdLineArgs.java:

public class CmdLineArgs {
    public void printArgs() {
        String[] args = Scratch2.getArgs();
        System.out.println ("Arg count is [" + args.length + "]");
        for (int i = 0; i < args.length; i++) {
            System.out.println ("Arg[" + i + "] is [" + args[i] + "]");
        }
    }
}

And, when run with the arguments a b c, this outputs:

Arg count is [3]
Arg[0] is [a]
Arg[1] is [b]
Arg[2] is [c]

Solution 2

The system-properties on some (?) JRE-implementations provide the system-property "sun.java.command" to get the programm-name and parameters that were used to start the program. Like "myjar.jar param1 param2 ...".

While this value doesn't even belong to the set of properties that are mentioned in the documentation, it is present in both Oracle-JRE v1.8 and OpenJRE v1.8 (tested).

I couldn't find any documentation whether this value is supported by default though (best I could find was the list in the System#getProperties() docs). Any clarification on this would be welcome. Handle with care!!!

Solution 3

If you don't care about OS portability, read /proc/self/cmdline or the equivalent for your OS.

See http://en.wikipedia.org/wiki/Procfs

Solution 4

As paxdiablo said, your main class would have to store these parameters and then either distribute or make available to needed ones. Often a good idea would be to let another class do the parsing of these parameters, and provide an object of this class instead of the raw command line to whoever needs it.

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