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Questions and Answers
What is the primary purpose of setters in a class?
What is the primary purpose of setters in a class?
Which of the following statements is true regarding getters?
Which of the following statements is true regarding getters?
What does a default constructor do when none is specified in the code?
What does a default constructor do when none is specified in the code?
In what scenario would a parameterized constructor be used?
In what scenario would a parameterized constructor be used?
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Which statement accurately describes the role of constructors in a class?
Which statement accurately describes the role of constructors in a class?
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Which principle states that a class should have only one responsibility?
Which principle states that a class should have only one responsibility?
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What does the Open/Closed Principle suggest about modifying a class?
What does the Open/Closed Principle suggest about modifying a class?
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In the context of design patterns, what is a common use case for the Factory Pattern?
In the context of design patterns, what is a common use case for the Factory Pattern?
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How should a class be designed according to the Dependency Inversion Principle?
How should a class be designed according to the Dependency Inversion Principle?
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Which pattern is not specifically mentioned as a variation of the Factory Pattern?
Which pattern is not specifically mentioned as a variation of the Factory Pattern?
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What does the annotation @BeforeEach indicate in JUnit 5?
What does the annotation @BeforeEach indicate in JUnit 5?
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Which assertion would you use to check if two values are equal in JUnit 5?
Which assertion would you use to check if two values are equal in JUnit 5?
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What is the purpose of the @AfterEach annotation in JUnit 5?
What is the purpose of the @AfterEach annotation in JUnit 5?
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In Java, what is a subclass in the context of inheritance?
In Java, what is a subclass in the context of inheritance?
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Which assertion can be used to check if an object is not null in JUnit 5?
Which assertion can be used to check if an object is not null in JUnit 5?
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What command is used to run tests in a Maven project?
What command is used to run tests in a Maven project?
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Which of the following is NOT a basic assertion in JUnit 5?
Which of the following is NOT a basic assertion in JUnit 5?
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What is the syntax used in Java to define a subclass that inherits from a superclass?
What is the syntax used in Java to define a subclass that inherits from a superclass?
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What is true about short-circuit evaluation when using the '&&' operator?
What is true about short-circuit evaluation when using the '&&' operator?
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Which of the following is a correct way to compare floating point numbers in Java?
Which of the following is a correct way to compare floating point numbers in Java?
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Which of the following primitive data types has the largest size in Java?
Which of the following primitive data types has the largest size in Java?
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In Java, which statement about class names is TRUE?
In Java, which statement about class names is TRUE?
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Which of the following statements regarding type casting is accurate?
Which of the following statements regarding type casting is accurate?
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What is a characteristic of static variables in Java?
What is a characteristic of static variables in Java?
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Which method is recommended to compare two String objects in Java?
Which method is recommended to compare two String objects in Java?
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Which of the following statements is TRUE regarding the boolean primitive data type in Java?
Which of the following statements is TRUE regarding the boolean primitive data type in Java?
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What role does the bartender play in the command pattern described?
What role does the bartender play in the command pattern described?
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Which of the following is NOT a benefit of using a composite structure?
Which of the following is NOT a benefit of using a composite structure?
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In the context of composite patterns, what is a Composite?
In the context of composite patterns, what is a Composite?
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When would you use a composite structure?
When would you use a composite structure?
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When a graphic is composed of smaller graphics, what is the graphic made up of termed?
When a graphic is composed of smaller graphics, what is the graphic made up of termed?
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What is the primary goal of using the Composite pattern?
What is the primary goal of using the Composite pattern?
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What corresponds to the Receiver in the command pattern described?
What corresponds to the Receiver in the command pattern described?
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Which of the following correctly describes a Leaf in the composite structure?
Which of the following correctly describes a Leaf in the composite structure?
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Study Notes
Short-Circuit Evaluation
- In an
||
expression, if the first operand is true, the entire expression is true and the second operand is not evaluated. - In an
&&
expression, if the first operand is false, the entire expression is false and the second operand is not evaluated. - Short-circuit evaluation can improve code efficiency and prevent runtime errors.
- It can prevent errors such as dividing by zero.
Comparisons
- Use the
==
operator for comparing primitive data types likeint
,boolean
, andchar
. - Avoid using
==
for comparing floating point numbers due to their inherent precision issues. Instead, useMath.abs(b - c) < epsilon
whereb
,c
, andepsilon > 0
are floating point types. - For comparing strings, use
StringObj.equals(Other_StringObj)
orStringObj.equalsIgnoreCase(Other_StringObj)
.
DataTypes
-
Primitive Data Types:
-
boolean
: 1 byte -
byte
: 1 byte -
char
: 2 bytes -
short
: 2 bytes -
int
: 4 bytes -
float
: 4 bytes -
double
: 8 bytes -
long
: 8 bytes
-
-
Derived Data Types:
-
array
-
function
-
-
User-Defined Data Types:
-
enum
-
class
-
Type Casting
- A value of one type can be assigned to a variable of any type further to the right in this hierarchy:
byte -> short -> int -> long
. - Values can also be cast in this order:
int -> float -> double
. - A value of type
char
can be assigned to a variable of typeint
.
Class
- Everything in Java must be in a class.
- The class name must match the filename exactly.
- All classes (directly or indirectly) inherit from the
Object
class, which contains thetoString()
method.
Static
- The
static
keyword can be used with variables, methods, classes, and blocks in Java. - Static variables and code are loaded into memory when the class is loaded.
Setters and Getters
-
Setters (Mutators):
- Used to set or update the value of a private field.
- Public access modifier.
- Have a
void
return type. - Can be used to (re)set individual attributes.
-
Getters (Accessors):
- Used to retrieve the value of a private field.
- Public access modifier.
- Have no parameters.
- Not required if specific attributes should not be exposed.
Constructors
- Constructors are special methods used for initializing object attributes.
- They have the same name as the class and do not have a return type.
- Types of constructors:
- Default Constructor: No parameters.
- Parameterized Constructor: At least one parameter.
- Copy Constructor: Creates a new object that is a copy of an existing object.
JUnit 5
-
BeforeEach Annotation:
- Runs a method before each test method in a class.
- Use to set up the test environment.
-
AfterEach Annotation:
- Runs a method after each test method in a class.
- Use to clean up after tests.
JUnit 5 Assertions
- assertTrue(test): Checks for a true condition.
- assertFalse(test): Checks for a false condition.
- assertEquals(expected, actual): Checks for equality between expected and actual values.
- assertNotEquals(unexpected, actual): Checks for inequality between expected and actual values.
- assertNull(value): Checks for null value.
- assertNotNull(value): Checks for non-null value.
Inheritance
- Inheritance is a mechanism for code reuse where a subclass inherits data and behavior from a superclass.
- The subclass extends the superclass using the
extends
keyword.
SOLID
-
SOLID is an acronym for the following design principles:
- Single Responsibility Principle (SRP): A class should have one and only one reason to change.
- Open/Closed Principle (OCP): A class should be open for extension, but closed for modification.
- Liskov's Substitution Principle (LSP): Subtypes should be substitutable for their base types.
- Interface Segregation Principle (ISP): Clients should not be forced to depend on methods they don't use.
- Dependency Inversion Principle (DIP): High-level modules should not depend on low-level modules. Both should depend on abstractions.
Factory
-
Factory Pattern:
- A creational design pattern that provides an interface for creating objects without specifying the concrete class.
- Used for creating different types of objects based on input.
Command Pattern
- Command Pattern: Separates the request from the execution of the request.
- Key Components:
- Client: Makes the request.
- Invoker: Handles the request.
- Receiver: Executes the actual request.
- Command: Encapsulates the request.
- ConcreteCommand: Defines the specific action to be executed.
Composite Pattern
-
Composite Pattern:
- Allows for recursive composition of objects.
- Provides a uniform way to handle both individual objects (leaf nodes) and composite objects (tree nodes).
- Key components:
- Component: Common interface for all objects.
- Leaf: Individual objects with no children.
- Composite: Objects with children.
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Description
This quiz covers key concepts in Java programming pertaining to short-circuit evaluation, comparisons, and primitive data types. It focuses on best practices for evaluating expressions and comparing variables in Java to improve code efficiency and accuracy. Ideal for students looking to solidify their understanding of these foundational programming concepts.