Arguments in Java function

Question

I'm trying to use another class to return data from another class. This class will either return a password, or a key, depending on the arguments sent to the class.

This is the function in the class that returns the data:

public static String main(String args[]){
        if (!args.equals(null)){
            String gen = generatePassword(args[1]);
            return gen;
        }else{
            String gen = generateRandomString();
            return gen;
        }
    }

My error is:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at me.GaryIsASloth.KeyGenerator.main(KeyGenerator.java:34)

With 34 referring to:

if (!args.equals(null)){

The arguments provided will either be "pass", following "true"/"false" which will tell the class whether to include special characters or not. Or for the key the args will be null.

I had the class working perfectly when I had it working with the key, and then after modification it worked fine with the password too. However I can't get it to work with both, dependant on the arguments. I've tried null check and length check. What can I do?

Mikhail Chibel · Accepted Answer · 2016-06-12T09:26:44.030

0

When checking for null you cannot check something.equals(null) as equals is a method and it cannot be called on null. Null is not an object. Secondly, elements in the arrays numbered starting from 0 so the first element will be arg[0].

public static String main(String args[]){
        String gen;
        if (args != null){
            gen = generatePassword(args[0]);
        }else{
            gen = generateRandomString();
        }
        return gen;
    }

edited Jun 12 '16 at 09:26

answered Jun 12 '16 at 09:19

Mikhail Chibel

1,865
1
22
34

`return gen != null ? generatePassword(args[0]) : generateRandomString();` is much cleaner imo – Idos Jun 12 '16 at 09:20
@Idos agree, but for beginners it could be too complicated. – Mikhail Chibel Jun 12 '16 at 09:27
@idos fix your suggestion – Mikhail Chibel Jun 12 '16 at 09:28
Maybe it is, but Stack Overflow caters to the general populous and not for the individual. – Idos Jun 12 '16 at 09:29
The reason why the (args[1]) was was used in the first selection was because it runs with the true/false arg, not the first one. – Jack Evans Jun 12 '16 at 09:31
@JackEvans, then getting the value is correct, it just looks suspicious as you don't use any other parameters in this method, so I thought it should be 0. – Mikhail Chibel Jun 12 '16 at 09:36

ΦXocę 웃 Пepeúpa ツ · Answer 2 · 2016-06-12T09:23:44.493

0

This here:

 if (!args.equals(null)){
            String gen = generatePassword(args[1]);
            return gen;

just because args is not null, does this mean it has 2 elements?

this here is not so a good idea:

String main(String[] args)

because java has a method that looks like that so that coincidence is not allowing you to compile

edited Jun 12 '16 at 09:23

answered Jun 12 '16 at 09:22

ΦXocę 웃 Пepeúpa ツ

47,427
17
69
97

This is not the OP's problem.. – Idos Jun 12 '16 at 09:22

score 0 · Answer 3 · answered Jun 12 '16 at 09:26

0

Instead of checking if (!args.equals(null)) do it like this if (args != null)

Then you should check if you have correct number of arguments, if you want to access args[1]

if(args.length == 2)

answered Jun 12 '16 at 09:26

Filoména Petržlénová

193
1
5
19

Arguments in Java function

3 Answers3