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Learning Exercise
In Java, the null literal is used to denote the absence of a value.
Primitive data types in Java all have a default value and therefore can never be null.
By convention, they start with a lowercase letter e.g int.
Reference types contain the memory address of an object and can have a value of null.
They generally start with an uppercase letter, e.g. String.
Attempting to assign a primitive variable a value of null will result in a compile time error as the variable always holds a primitive value of the type assigned.
//Throws compile time error stating the required type is int, but null was provided
int number = null;
Assigning a reference variable a null value will not result in a compile time error as reference variables are nullable.
//No error will occur as the String variable str is nullable
String str = null;
In this exercise you'll be writing code to print name badges for factory employees.
Employees have an ID, name and department name. Employee badge labels are formatted as follows: "[id] - name - DEPARTMENT".
Implement the Badge.print() method to return an employee's badge label:
Badge badge = new Badge();
badge.print(734, "Ernest Johnny Payne", "Strategic Communication");
// => "[734] - Ernest Johnny Payne - STRATEGIC COMMUNICATION"
Note that the department should be uppercased on the label.
Due to a quirk in the computer system, new employees occasionally don't yet have an ID when they start working at the factory.
As badges are required, they will receive a temporary badge without the ID prefix. Modify the Badge.print() method to support new employees that don't yet have an ID:
Badge badge = new Badge();
Badge.print(null, "Jane Johnson", "Procurement");
// => "Jane Johnson - PROCUREMENT"
Even the factory's owner has to wear a badge at all times.
However, an owner does not have a department. In this case, the label should print "OWNER" instead of the department name.
Modify the Badge.print() method to print a label for the owner:
Badge badge = new Badge();
badge.print(254, "Charlotte Hale", null);
// => "[254] - Charlotte Hale - OWNER"
Note that it is possible for the owner to also be a new employee:
Badge badge = new Badge();
badge.print(null, "Charlotte Hale", null);
// => "Charlotte Hale - OWNER"
Edit via GitHub
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