What are wrapper classes?

Wrapper class is a wrapper around a primitive data type. It represents primitive data types in their corresponding class instances e.g. a boolean data type can be represented as a Boolean class instance. All of the primitive wrapper classes in Java are immutable i.e. once assigned a value to a wrapper class instance cannot be changed further.

Wrapper Classes are used broadly with Collection classes in the java.util package and with the classes in the java.lang.reflect reflection package.