Command line arguments not being properly recognized

Question

In my program I'm trying to loop specific actions depending on the value of the String args[0]. I have a conditional tree setup, but no matter what args[0] is, it always chooses the last else option as opposed to the option I want it to be.

Here is the relevant code:

public static void main(String[] args)
{
    int a = Integer.parseInt(args[1]);
    int b = Integer.parseInt(args[2]);
    int c = Integer.parseInt(args[3]);
    int d = Integer.parseInt(args[4]);

    for (int i = -a; i <= a; i++)
    {
        for (int j = -b; j <= b; j++)
        {
            for (int k = -c; k <= c; k++)
            {
                for (int l = -d; l <= d; l++)
                {
                    if (args[0] == "rational-class")
                        rationalClass(a,b,c,d);
                    else if (args[0] == "rational-instance")
                        rationalInstance(a,b,c,d);
                    else if (args[0] == "complex-class")
                        complexClass(a,b,c,d);
                    else if (args[0] == "complex-instance")
                        complexInstance(a,b,c,d);
                    else
                        System.out.println("error");
                }
            }
        }
    }

}

String comparisons with '=='; try using .equals – crownedzero Nov 04 '13 at 20:43 — crownedzero, Nov 04 '13 at 20:43

score 1 · Answer 1 · answered Nov 04 '13 at 20:44

1

Try comparing the two strings with equals method, i.e.

if (args[0].equals("rational-class")

answered Nov 04 '13 at 20:44

user2927391

197
2
11

1

As a general note, it's safer to do comparisons with the constant first, e.g. `"rational-class".equals(args[0])` as a well-defined equals method will not throw a NullPointerException but args[0] may be null. – drobert Nov 04 '13 at 20:47
aaaaaand I feel silly Thanks man, it worked like a charm. – Christian Baker Nov 04 '13 at 20:47
1

it happens... Good Luck, bro.. – user2927391 Nov 04 '13 at 20:53

score 0 · Answer 2 · answered Nov 04 '13 at 20:48

0

If it's a string that you are comparing for you arg[0], you need to do something like this.

    args[0].equals("......")

answered Nov 04 '13 at 20:48

Command line arguments not being properly recognized

2 Answers2