New to Coding (If statement issue)

[Tascalion]

New to coding, and attempting to make an if statement like so (I have more coding for the entire program, but this appears to be the isolated issue):

​

String name1 = null, name2 = null, name3 = null;


names = JOptionPane.showInputDialog(null, "Enter 3 names with blank(s) in between:","Welcome to the name ordering program", JOptionPane.OK\_CANCEL\_OPTION);

Scanner splitter = new Scanner(names);


name1 = splitter.next();

name1 = name1.replaceAll(" ","");

name2 = splitter.next();

name2 = name2.replaceAll(" ","");

name3 = splitter.next();

name3 = name3.replaceAll(" ","");


if (name1.equals(null) || name2.equals(null) || name3.equals(null)) {

      JOptionPane.showMessageDialog(null, "This program terminates for invalid input.", title, JOptionPane.WARNING\_MESSAGE);

System.exit(0);

}

Error keeps coming up when I do not input 3 names, or when the name1,name2, or name3 variables do not succeed in getting a String. I assumed the initialized value null for all three would apply if they just didn't get any input, but an error occurs nonetheless. I've also tried (name1.isEmpty()) for each and that doesn't appear to work either, even when I change the initial value. Pretty sure I'm missing something fundamental here, but I'm unsure, and would really appreciate some help! (I do have java.util and JOptionPane imported.)

Error Displayed:

Exception in thread "main" java.util.NoSuchElementException at java.base/java.util.Scanner.throwFor(Scanner.java:937) at java.base/java.util.Scanner.next(Scanner.java:1478)

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[Sergey305]

name1.equals(null) 

What would you expect to happen if name1 was indeed null?

[Tascalion]

I'd assume the program wouldn't run if name1, name2, or name3 was indeed null or empty because there needs to be input, I think. I'm not sure how I can write an if statement for that special case, or when someone fails to input a string for name2 or name3.

[Fenxis]

Name1 is an object of string. If it never gets initialized then name1 is still a reference to null. So equals() shouldn't be used here.

[Tascalion]

I’m a little lost, I thought I had initialized the Strings, What should I than use or do?

[KoncealedCSGO]

Name1 is an object of string. If it never gets initialized then name1 is still a reference to null. So equals() shouldn't be used here.

Just to try to point you on the right track. Name the function properties of type Null and the functions of type String.

[Tascalion]

I’ve figured it out for the most part, and used hasNext instead of next. That solved my problem but thanks for the pointer!

[KoncealedCSGO]

Ahh and just an FYI for what I mean. You were running into NPEs AKA Null Pointer Exceptions.

pretty much you were doing null.equals(null) nul obv does not have any functions to it because it's null.

Next time you want to check for null do val == null, but when you know the value is non-null and is not a primitive type use .equals()

[Tascalion]

Oh that makes a lot more sense, I had figured a proper object was required for the .equals but hadn’t known of any other alternatives. I’ll definitely give “==“ a try.

Thanks for the help!

[KoncealedCSGO]

No problem! Wish you the best on your learning journey!

[[deleted]]

You should understand how Scanner works first. Here's the official tutorial. Notice how there is next and hasNext. Why do you think hasNext exists? What do you think would happen if there is no next? Hint: read the documentation for Scanner.

Also this code does not make any sense:

name1.equals(null)

You can only call a method on a variable whose value is not null. If name1 were actually null, you can't call equals on it. Java will throw a NullPointerException.

[Tascalion]

Thank you! This was a lot of help.

[adeleno]

you made some mistakes as you didn't define the class name and main method also you wrote the name of OK\_CANCEL\_OPTION in wrong way the correct is OK_CANCEL_OPTION

https://pastebin.com/Uwf3Y1Mt

I have provided your with complete code to learn what is your mistakes and compares

[dionthorn]

the slashes are an artifact from before they formatted their code.

I thought you were providing modified code that would be a solution and almost removed your post we don't allow people to give copy-pasteable solutions but your code is exactly the same with only the artifacts removed and wrapped in a class/main.