Passing -d option in java

Question

I am solving a question where the requirement is that the program should allow the user to set a parameter with the -d command-line option. Does java provide any mechanism to pass argument with -d option? I couldn't find any so I am interpreting this as if the command line option value is -d, that means that user wants to enter the parameter next.

if ( args[0].equals("-d") )
{
     parameter = args[0];
}

Is this right way to check that? Is there some better way to check whether user has entered -d option? Does java provides some other mechanism for that?

Use a command line argument parser. [JCommander](http://jcommander.org/) (no affiliation) is my preference - there are others. — Boris the Spider, Jul 30 '16 at 08:40
Then `parameter = "-d"`, or `null` - is that what you want? Have a look at Apache Commons CLI for example; and http://stackoverflow.com/questions/10745811/how-to-use-terminal-arguments-with-values-in-java — Has QUIT--Anony-Mousse, Jul 30 '16 at 08:51

score 2 · Answer 1 · answered Jul 30 '16 at 08:46

I think the requirement means -D (the capital one), not -d. Such options are used to pass additional parameters to java. For instance, -Dmy.option=value. In such case you have access to this property by means of System class:

String myOption = System.getProperty("my.option");

score 1 · Answer 2 · answered Jul 30 '16 at 08:41

1

What if someone runs the program with ./yourapp something else -d? Now the argument -d exists, but not on position 0

So, my recommendation is to loop through all of the arguments and check what you need.

int i;
boolean dParam = false;
for (i = 0; i < args.length; i++) {
    if (args[i].equals("-d")) {
        dParam = true;
    }
}

If you want the user to input something after the -d, like a filename then I would recommend doing this:

int i;
boolean dParam = false;
String dParamValue;

for (i = 0; i < args.length; i++) {
    if (args[i].equals("-d")) {
        dParam = true;
        dParamValue = args[++i];
    }
}

answered Jul 30 '16 at 08:41

Ibrahim

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This is beginning to look at lot like reinventing a wheel. Yours is somewhat square at best... – Boris the Spider Jul 30 '16 at 08:42
It's not reinventing the wheel. It's an updated version of OP's initial code that works. – Ibrahim Jul 30 '16 at 08:49

score 0 · Answer 3 · edited Jun 20 '20 at 09:12

All parameters you pass to the program you are running, are going in the application throug the parameter String[] args in the main method..

You can then check if the dictionary is there requested, by just checking if the array of arguments contains that key..

Example:

public static void main(String[] args) {
System.out.println("is dictionary there?: " + Arrays.asList(args).contains("d"));

if (Arrays.asList(args).contains("d")) {
    prepateDictionary();
}else {
    prepareSomethingElse();
}

}

Passing -d option in java

3 Answers3

Example: