b$.$In the class Safe add two private fields:

state, which is of type SafeState, and will be used to control the state of the safe.

maxItems, an int representing the maximum number of items that can be stored in the safe.

Also add a public field $($for testing purposes$)$:

contents, which is an ArrayList of String, used to keep a record of items in the Safe.

Remember that you will require an import statement above your class in order to use an ArrayList.

$(3$ marks$)$

c$.$Add a public constructor that receives one parameter of type int called aMaxItems. In the constructor body:

state should be initialised to a new SafeState object.

contents should be set to an empty collection of the appropriate type.

maxItems should be set to the number of items the safe can hold, received as a parameter.