Immutable types are types that when changed create a new version of the object in memory, rather than changing the existing object in memory. The simplest example of this is the built-in
Taking the following code, that appends " world" onto the word "Hello"
string myString = "hello"; myString += " world";
What is happening in memory in this case is that a new object is created when you append to the
string in the second line. If you do this as part of a large loop, there is the potential for this to cause performance issues in your application.
The mutable equivalent for a
string is a
Taking the following code
StringBuilder myStringBuilder = new StringBuilder("hello"); myStringBuilder.append(" world");
When you run this, you are modifying the
StringBuilder object itself in memory.