Java calling method and using ternary operator and assign in the parameters

javamethod-callternaryvariable-assignment

I was reviewing some code and I came across this:

 public static doSomething(String myString, String myString2) {
        //Stuff
 }

 public static doAnotherThing(String myString) {
      return doSomething(myString = myString != null ? myString.toLowerCase(): myString, null)
 }

How is this working exactly?, I know the .toLowerCase resulting string is assigned to myString (yes I know bad practice since you are not supposed to reassign method parameters in fact they should be final), but I am not quite sure how does the method always receives the 2 parameters it needs.

I know how it works when myString is null or at least I think I do, since the ternary has myString, null, but I am not quite sure why it would go there when myString is not null?.

Best Answer

Parenthesis to the rescue!

doSomething(myString = ( ( myString != null ) ? myString.toLowerCase() : myString ), null)

To understand this, you need to know two things:

  • How the ternary operator works
  • The fact that the assignment operator returns the thing it is assigning
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