What does it mean when there is a -- before an in value in java? Also what is a StringBuilder

Question

I am trying to finish an assignment in my intro to Java course, and I have some questions. First off, what does it mean when there is a -- in FRONT of an int value? Also what is a String Builder? I had some help but want to understand what it is I'm using in the code. Thanks.

Answer 1

-- is a predecrement

Java StringBuilder class is used to create mutable (modifiable) string. A String is immutable i.e string cannot be changed once created and everytime a value is change it create new string.

But in case of StringBuilder which is mutable string can change.