Types and Method Overriding in Programming

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Questions and Answers

What is another name for declared type?

Static type (correct)

Interface type

Dynamic type

Constructor

What is another name for object type?

Primitive type

Dynamic type (correct)

Static type

Reference type

How do you override a method?

Must be a class extending a class; use @override; keep the same method header, change method body.

What does 'extends' mean in programming?

Relationship between two classes or two interfaces; retains method bodies for classes and method contracts for interfaces. Signup and view all the answers

A class ___________s an interface.

implements Signup and view all the answers

What kind of variable is NaturalNumber?

A reference type that points to an object value. Signup and view all the answers

How do I initialize a natural number with a number bigger than the max value of an int?

Use another natural number, a string with said number, or math to get there. Signup and view all the answers

What is the default parameter mode when none is specified?

Restores Mode. Signup and view all the answers

What does restores mean?

Returns input variable to its original value at the end of the method. Signup and view all the answers

What does updates mean?

Changes the value of the input variable based on its original value. Signup and view all the answers

What does clears mean?

Returns the value of the input variable to a default value, usually zero. Signup and view all the answers

What are the results of NaturalNumber compareTo?

Positive if A > B, 0 if A = B, Negative if A < B. Signup and view all the answers

What does replaces mean?

Changes the value of the input variable regardless of the original value. Signup and view all the answers

What is an immutable reference?

Has a reference value and an object value; cannot be changed by a method call. Signup and view all the answers

What is a mutable reference?

Has a reference value and an object value; can be changed by methods. Signup and view all the answers

Which of the following are primitive types?

Boolean Signup and view all the answers

Test cases should include which of the following?

All of the above Signup and view all the answers

What does overloading a method mean?

A method that appears multiple times within a class, with different argument types and/or number of arguments. Signup and view all the answers

What kind of error does infinite recursion induce?

Stack Overflow Error. Signup and view all the answers

What can a failed test case indicate?

All of the above Signup and view all the answers

What is best practice for declaring variables?

Left side should be declared type, right side should be object type. Signup and view all the answers

What does TransferFrom do?

Copies value and clears value of the one it copies from. Signup and view all the answers

What are the characteristics of NaturalNumber?

Must be positive; mutable type; unlimited upper bound; uses integer math. Signup and view all the answers

What is a string's characteristic?

Reference type, but immutable; cannot be changed by a method call. Signup and view all the answers

What is an array?

Reference type; mutable. Signup and view all the answers

What does NaturalNumber.newInstance() method do?

Creates a new natural number of the same type, set to an initial value (0); is not an alias. Signup and view all the answers

What is a string permutation?

Reordering of the same values. Signup and view all the answers

What does freelunch teach you about recursion?

To do recursion correctly, you must call the method within itself using a smaller version of the problem. Signup and view all the answers

What are static methods?

By itself, no 'this'; can return any type or nothing (void). Signup and view all the answers

What are instance methods?

Use 'this'; 'this' is a receiver. Signup and view all the answers

What is confidence building recursion argument like?

Mathematical proof by induction. Signup and view all the answers

What does DivideBy2 do?

Shave off a digit, divide it, recurse with a smaller number, and multiply that number by 10 adding remainder. Signup and view all the answers

What can JUnit do?

It can show the presence of a defect; cannot prove correctness or show the absence of defects. Signup and view all the answers

What is NaturalNumber adding itself dividing?

Do division first; add restores the argument input after adding two. Signup and view all the answers

Why isn't aliasing a problem with immutable types?

Because object values cannot be changed; changing the alias points to a new object. Signup and view all the answers

What is a reference type?

Reference points to an object; reference value = memory address of object. Signup and view all the answers

What is a substring?

Starts from initial value and goes to the value before end value. Signup and view all the answers

What is unit testing?

Testing individual units or components. Signup and view all the answers

What is integration testing?

Testing multiple components put together. Signup and view all the answers

What is system testing?

Testing a whole end-user system. Signup and view all the answers

What should the actual behavior of a method be?

A subset of allowed behaviors. Signup and view all the answers

Study Notes

Types in Programming

Declared Type (Static Type)
- Fixed type at the declaration level
- Remains constant during program execution
Object Type (Dynamic Type)
- Type that can change at runtime
- Defined on the right side of a declaration
- Constructors can instantiate the object type
- Supports interface implementations and overridden methods

Method Overriding

Requires a subclass to extend a superclass
Use the @override annotation
Maintain the same method header while modifying the body

Class and Interface Relationships

Extends: Describes the inheritance relationship
- Classes retain method bodies; interfaces retain contracts
Implements: Defines how a class uses an interface
- A class can implement multiple interfaces

Variable Types

NaturalNumber
- Reference type that points to an object
- Must always be positive
- Supports unlimited upper bounds and uses integer math
Mutable Reference: Example includes NaturalNumber and arrays. Their values can be changed.
Immutable Reference: Example includes strings. Their values cannot be altered within methods.

Method Parameter Modes

Restores: Returns input variable to its original state after method execution.
Updates: Alters the value of the input variable based on its initial state.
Clears: Resets the value of the input variable to a default (usually zero).
Replaces: Overrides the original variable value without regard for its previous state.

Method Characteristics

Overloading: Same method name with different parameter types or counts within a class.
Static Methods: Can be invoked without a class instance; do not use this.
Instance Methods: Require an object instance; utilize this to refer to the current object.

Testing Practices

Test Cases: Should include routine, challenging, and boundary cases, all satisfying preconditions.
Unit Testing: Focuses on individual components.
Integration Testing: Examines combined components for correctness.
System Testing: Evaluates the complete system from an end-user perspective.
Failed Test Cases: May suggest a bug in code, a faulty test case, or broken preconditions.

Recursive Methods

Infinite Recursion: Leads to a stack overflow error.
Confidence Building Argument: Analogous to mathematical proof by induction.
Freelunch Principle: Requires recursive calls with smaller problem instances.

Additional Concepts

TransferFrom Method: Copies value from one variable and clears the source.
String Permutation: Involves reordering elements of a string.
Substring Function: Extracts part of a string from start index to end index minus one.

Aliasing and Reference Types

Immutable Types: Aliasing doesn't pose risks; any modification results in a new reference.
Reference Type: Consists of a memory address pointing to an object; changing the reference updates the address, not the object.

Miscellaneous

Default Parameter Mode: Restores to default state when not explicitly defined.
Junit: A testing framework that identifies defects but does not confirm overall correctness.

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Description

This quiz explores concepts related to declared types, object types, and method overriding in programming. Additionally, it covers relationships between classes and interfaces, including the use of annotation in method overriding. Test your understanding of these fundamental programming principles.