1.12 Objects: Instances of Classes

Suggested Skills: 4.A

LO 1.12.A — Explain the relationship between a class and an object.

• 1.12.A.1 — An object is a specific instance of a class with defined attributes. A class is the formal implementation, or blueprint, of the attributes and behaviors of an object.

• 1.12.A.2 — A class hierarchy can be developed by putting common attributes and behaviors of related classes into a single class called a superclass. Classes that extend a superclass, called subclasses, can draw upon the existing attributes and behaviors of the superclass without replacing these in the code. This creates an inheritance relationship from the subclasses to the superclass.

  • ❌ EXCLUSION — Designing and implementing inheritance relationships are outside scope.

• 1.12.A.3 — All classes in Java are subclasses of the Object class.

LO 1.12.B — Develop code to declare variables to store reference types.

• 1.12.B.1 — A variable of a reference type holds an object reference, which can be thought of as the memory address of that object.