Why are immutable objects used in programming?

Immutable objects are objects whose state cannot be changed after creation. In programming, they are used for:

• Ensuring thread safety, as immutable objects do not require synchronization.
• Simplifying debugging and testing, since the object's state is stable.
• Using as keys in collections, such as in HashMap.

In Java, an example of an immutable object is the String class. Once a string is created, its content cannot be changed, which prevents many errors and improves performance through caching.