Use boolean rather than Boolean every time you can. This will avoid many NullPointerExceptions and make your code more robust.
Boolean is useful, for example
- to store booleans in a collection (List, Map, etc.)
- to represent a nullable boolean (coming from a nullable boolean column in a database, for example). The null value might mean “we don’t know if it’s true or false” in this context.
- each time a method needs an Object as argument, and you need to pass a boolean value. For example, when using reflection or methods like
MessageFormat.format().