STI IT1712 Classes and Methods Quiz

Classes and Methods

• The void keyword indicates that a method does not return a value.
• A parameter is a list of variables in a method declaration, while an argument is the actual value passed when the method is invoked.
• The data type of the return value must match the declared return type.

Instance Variables and Local Variables

• Instance variables are variables declared outside a method, constructor, or block.
• Local variables are variables declared within a method definition and are only visible to that method.

The this Keyword

• The this keyword represents the object's name receiving the method call within a method definition.

Information Hiding and Encapsulation

• Information hiding is a mechanism for restricting access to some of an object's components.
• Advantages of information hiding include:
  • Making components easier to understand and use
  • Simplifying modification and repair
  • Facilitating re-use
• If an instance variable is public, there are no restrictions on where its name can be used.
• If an instance variable is private, its name cannot be used to access it outside of the class definition.
• Accessor methods are public methods that return data from private instance variables.
• Mutator methods are public methods that change the data stored in one or more private instance variables.

Encapsulation

• Encapsulation is the process of combining data and actions into a single item.
• It groups instance variables and methods into a class and hides implementation details.

UML Class Diagram

• The UML Class Diagram describes the structure of a class by displaying the class name, variables, and methods.

Objects and References

• A variable of a class type contains the memory address of the object named by the variable, rather than the object itself.
• The address of the object's memory location is called a reference to the object.
• Class types are reference types whose variables hold references or memory addresses.
• Use the equals() method for comparison, instead of ==.