Groovy String concatenation with null checks

concatenationgroovynullstring

Is there a better way to do this? Note: part1, part2 and part3 are string variables defined elsewhere (they can be null).

def list = [part1, part2, part3]
list.removeAll([null])
def ans = list.join()

The desired result is a concatenated string with null values left out.

Best Answer

You can do this:

def ans = [part1, part2, part3].findAll({it != null}).join()

You might be able to shrink the closure down to just {it} depending on how your list items will evaluate according to Groovy Truth, but this should make it a bit tighter.

Note: The GDK javadocs are a great resource.

Related Solutions

C# – the difference between String and string in C#

string is an alias in C# for System.String.
So technically, there is no difference. It's like int vs. System.Int32.

As far as guidelines, it's generally recommended to use string any time you're referring to an object.

e.g.

string place = "world";

Likewise, I think it's generally recommended to use String if you need to refer specifically to the class.

e.g.

string greet = String.Format("Hello {0}!", place);

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

Javascript – How to check for an empty/undefined/null string in JavaScript

If you just want to check whether there's a truthy value, you can do:

if (strValue) {
    //do something
}

If you need to check specifically for an empty string over null, I would think checking against "" is your best bet, using the === operator (so that you know that it is, in fact, a string you're comparing against).

if (strValue === "") {
    //...
}

Best Answer

Related Solutions

C# – the difference between String and string in C#

This is the style that Microsoft tends to use in their examples.

Javascript – How to check for an empty/undefined/null string in JavaScript

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