What is immutability and why should I worry about it?

Question

I\'ve read a couple of articles on immutability but still don\'t follow the concept very well.

I made a thread on here recently which mentioned immutability, but as

Answer 1

"... why should I worry about it?"

A practical example is repetitive concatenation of strings. In .NET for example:

string SlowStringAppend(string [] files)
{
    // Declare an string
    string result="";

    for (int i=0;i

Unfortunately using the first (slow) function approach is still commonly used. An understanding of immutability makes it very clear why using StringBuilder is so important.