how to check if the variable is null?

Question

I know this doesnt work but how can I know if the user added even one char?

public class Program
import java.util.Scanner;
{
public static void main(String[] args) {
    Scanner a = new Scanner(System.in);
    String b = a.nextLine();

//I know this doesnt work but how can I know if the user added even one char?
    if (b!=null){
    System.out.println(b);
}
}
}

Solution

you can use .equals("") or .isEmpty()

check check if the variable is null

Comments

[Fildor]

You can check String.length ... and String.isEmpty() is equivalent to checking length for 0.

[Andy Turner]

b.isEmpty(). nextLine() never returns null.

[Fildor]

Mind that Whitespaces count for length. So if you actually want to check for "Non-Whitespace characters" then there is a little more effort. See also: stackoverflow.com/a/3247081/982149

[Andy Turner]

The b != null is redundant.

[Sync]

Why you'd even suggest equals("") when String has isEmpty() is beyond me.

[useless'MJ]

because you can use equals("") also as it is from parent calss Object but you are right , better to use isEmpty() because ,see The main benefit of "".equals() is you don't need the null check (equals will check its argument and return false if it's null), which you seem to not care about. If you're not worried about b being null (or are otherwise checking for it), I would definitely use .isEmpty(); it shows exactly what you're checking, you care whether or not b is empty, not whether it equals the empty string

[Sync]

Your answer advocates .equals("") not "".equals(s). It also did not include the advantages of using "".equals(s). Are you expecting this to come naturally to the readers who read your answer but not the comments? I still stand by that this is a bad answer.

[useless'MJ]

i am not telling you the advantages am telling you how many ways we can check..so .equals() is also one of them