通过方法传递数组（java命令行参数）

Question

I was wondering how I could check args.length within a method.

For example:

public static void commandLineCheck (int first, int second){
    if (args.length==0){
        //do something with first and second
    }
}

public static void main(String[] args) {
    int first = Integer.parseInt(args[0]);
    int second = Integer.parseInt(args[1]);
    commandLineCheck(first, second);
}

I get a "cannot find symbol: args" error when I do this. Right now, I'm thinking I need to pass args[] through the method as well. I've tried this but it then gives me an "" error. Is there a beginner-friendly solution to this?

EDIT: Thank you so much for the quick response guys! It worked!

Answer 1

Change your code like this (You need to pass the array's parameter to your check method)

public static void commandLineCheck (int first, int second, String[] args){
    if (args.length==0){
        //do something with first and second
    }
}

public static void main(String[] args) {
    int first = Integer.parseInt(args[0]);
    int second = Integer.parseInt(args[1]);
    commandLineCheck(first, second, args);
}

And it will work. However the following test (args.length==0) does not make much sense since you have already assumed that args.length is greater or equal to 2 by extracting two values from it inside the main method. Therefore when you get to your commandLineCheck method, this test will always be false.

Answer 2

You need to pass the String [] args to your commandLineCheck method. This is written the same way as you declare the array for your main method.

public static void commandLineCheck (String[] args){
    if (args.length==0){
        //do something with first and second
    }
}

Also you probably want to change your main method and commandLineCheck method a bit.

public static void commandLineCheck(String [] args) {
    /* make sure there are arguments, check that length >= 2*/
    if (args.length >= 2){
        //do something with first and second
        int first = Integer.parseInt(args[0]);
        int second = Integer.parseInt(args[1]);
    }
}

public static void main(String[] args) {
    commandLineCheck(args);
}