Midterm Review Flashcards

Question

Describe encapsulation and how would you use it in a project?

Answer 1

Encapsulation is the concept of wrapping data and methods into a single unit, typically a class, and restricting direct access to some of the object's components. Use encapsulation to protect data integrity and provide controlled access through getter and setter methods.

Answer 2

The four access levels are: * public: Accessible from anywhere. * protected: Accessible within the same package and subclasses. * default (no modifier): Accessible only within the same package. * private: Accessible only within the same class.

Answer 3

Getter and setter methods provide controlled access to private fields of a class, allowing for encapsulation and data validation while maintaining the integrity of the object.

Answer 4

Use an interface when you need to define a contract that multiple classes can implement, especially if the classes do not share a common base class. Interfaces support multiple inheritance, unlike abstract classes.

Answer 5

SOLID principles are guidelines for object-oriented design: * S: Single Responsibility Principle (SRP) * O: Open/Closed Principle (OCP) * L: Liskov Substitution Principle (LSP) * I: Interface Segregation Principle (ISP) * D: Dependency Inversion Principle (DIP) They are important for creating maintainable, flexible, and scalable code.

Answer 6

Maven is a build automation tool used primarily for Java projects. It simplifies project builds, dependency management, and project documentation through a standardized approach and a POM (Project Object Model) file.

Answer 7

SDLC (Software Development Life Cycle) is a process used for planning, creating, testing, and deploying software. It is important for ensuring systematic, organized, and efficient development.

Answer 8

Use Agile when projects require flexibility, frequent updates, and customer feedback. Use Waterfall for projects with well-defined requirements and a clear, linear progression.

Answer 9

Maven build lifecycle phases include: * validate: Validate the project structure and configuration. * compile: Compile the source code. * test: Run tests. * package: Package the compiled code into a distributable format. * verify: Perform any additional verification. * install: Install the package into the local repository. * deploy: Deploy the package to a remote repository.

Answer 10

The POM.xml (Project Object Model) file is the core configuration file in a Maven project. It defines project dependencies, build configurations, and plugins, and manages project information and settings.

Answer 11

Source control management (SCM) tracks and manages changes to source code over time. It is useful for versioning, collaboration, and maintaining a history of code changes.

Answer 12

Main sections of a Git project include: * Working Directory: The current files you are working on. * Staging Area (Index): Where you prepare files to be committed. * Repository: Where committed files are stored.

Answer 13

Common Linux commands include: * ls: List directory contents. * cd: Change directory. * cp: Copy files or directories. * mv: Move or rename files or directories. * rm: Remove files or directories. * chmod: Change file permissions. * grep: Search for text in files.

Answer 14

Common Git operations include: * git init: Initialize a new repository. * git clone: Clone a repository. * git add: Stage changes for commit. * git commit: Commit staged changes. * git push: Push commits to a remote repository. * git pull: Fetch and merge changes from a remote repository. * git branch: List or create branches. * git merge: Merge branches.

Answer 15

Declaring a variable means defining its type and name, while assigning a variable involves initializing it with a value. Declaration and assignment can occur together or separately.

Answer 16

A pair of curly braces {} defines a block of code, such as the body of a method or class.

Answer 17

Source code is the human-readable code written in a programming language. Bytecode is the intermediate code generated by a compiler that can be executed by a virtual machine, such as the Java JVM.

Answer 18

Creating a method involves defining its signature (return type, name, parameters) and body. Calling a method involves using its name and passing required arguments.

Answer 19

A method is a block of code that performs a specific task and can be called upon to execute. It may take parameters and return a value.

Answer 20

A variable is a storage location identified by a name and used to hold data that can be modified during program execution.

Answer 21

* JVM (Java Virtual Machine): Executes Java bytecode. * JRE (Java Runtime Environment): Provides the JVM and standard libraries needed to run Java applications. * JDK (Java Development Kit): Includes the JRE and development tools like compilers and debuggers for developing Java applications.

Answer 22

A conditional statement controls the flow of execution based on whether a condition is true or false, using constructs like if, else, else if, and switch.

Answer 23

Common loops include: * for: Repeats a block of code a specific number of times. * while: Repeats a block of code while a condition is true. * do-while: Similar to while, but guarantees the block executes at least once.

Answer 24

The main method is the entry point of a Java application. It must be defined as public static void main(String[] args).

Answer 25

Primitive datatypes are basic data types provided by Java. Examples include: * int: Integer values. * double: Floating-point numbers. * char: Single characters. * boolean: True or false values.

Answer 26

Shorthand assignment operators combine an arithmetic operation with assignment, such as +=, -=, *=, /=, %=.

Answer 27

The modulo operator % returns the remainder of a division operation. It is useful for determining if a number is divisible by another or for cyclic operations.

Answer 28

Increment (++) and decrement (--) operators increase or decrease a variable's value by one, respectively. They can be used in prefix (++var) or postfix (var++) forms.

Answer 29

You can iterate over an array using a for loop or an enhanced for loop. Example: java Copy code for (int i = 0; i < array.length; i++) { // Access array[i] } or java Copy code for (int element : array) { // Access element }

Answer 30

An array is a data structure that stores a fixed-size sequence of elements of the same type. It is useful for efficiently storing and accessing multiple values using indices.

Answer 31

A stacktrace provides information about the call stack at the point an exception was thrown. It helps identify the sequence of method calls leading to the error, aiding in debugging.

Answer 32

A stacktrace provides information about the call stack at the point an exception was thrown. It helps identify the sequence of method calls leading to the error, aiding in debugging.

Answer 33

The Scanner class is used for reading input from various sources, including user input from the console. Example: java Copy code Scanner scanner = new Scanner(System.in); String input = scanner.nextLine();

Answer 34

Use a switch statement when you have multiple discrete values to compare against a single variable, as it can be more readable and efficient.

Answer 35

Use an if statement for complex conditions or when dealing with ranges or non-discrete values. Use switch for cleaner code with discrete values, such as enumerations or constants.

Answer 36

An operating system is software that manages hardware resources and provides services for computer programs. It acts as an intermediary between users and the computer hardware.

Answer 37

"Full stack" refers to the complete set of technologies and layers required to develop a complete application, including both frontend (client-side) and backend (server-side) components.

Answer 38

The String datatype represents text in Java.

Answer 39

Use the length property to access the last value: java Copy code array[array.length - 1]

Answer 40

Check the error message and stacktrace for clues, review the code at the indicated line, ensure there are no syntax errors, and use debugging tools to inspect variables and execution flow.

Answer 41

Verify the logic of your code, check input values and assumptions, use print statements or a debugger to trace execution, and test individual components to isolate the issue.

Answer 42

Creating methods helps modularize code. For example, a method calculateArea() can be used to compute the area of a shape, improving code reusability and readability.

Answer 43

The compilation process converts Java source code into bytecode using the javac compiler. The bytecode is then executed by the JVM.

Answer 44

Basic entities include: * Classes: Blueprints for creating objects. * Objects: Instances of classes. * Methods: Functions defined within classes. * Variables: Storage for data.

Answer 45

Benefits of Java include platform independence (write once, run anywhere), strong community support, rich standard libraries, and robust security features.

Answer 46

Flow control statements manage the execution order of code, including conditional statements (if, switch) and loops (for, while, do-while).

Answer 47

A package is a namespace that organizes related classes and interfaces. It helps in managing code modularity, avoiding name conflicts, and improving maintainability.

Answer 48

A fully qualified class name includes the package name and the class name, such as com.example.MyClass.

Answer 49

Use the equals() method to compare strings: java Copy code if (input.equals("yes")) { // Do something }

Answer 50

An instance variable is unique to each object instance, while a static variable is shared across all instances of a class.

Answer 51

Review the error message and stacktrace, check for syntax errors or exceptions, and use debugging tools to inspect the code and execution flow.

Answer 52

An instance method requires an object to be called and can access instance variables. A static method can be called on the class itself and can only access static variables.

Answer 53

Scopes in Java include: * Local Scope: Within a method or block. * Instance Scope: Within an instance of a class. * Class Scope: For static variables and methods within a class.

Answer 54

Variables defined within a method are local to that method and cannot be accessed outside. To access data outside, use instance variables or return values from the method.

Answer 55

Classes are used to create objects, define data structures, and encapsulate methods and variables that operate on the data.

Answer 56

An object is an instance of a class that encapsulates data (attributes) and methods (functions) that operate on the data.

Answer 57

Garbage collection automatically reclaims memory occupied by objects that are no longer in use, helping manage memory efficiently and preventing memory leaks.

Answer 58

An array is a fixed-size collection of elements of the same type, while an ArrayList is a resizable collection from the Java Collections Framework.

Answer 59

Errors are severe issues not typically handled by applications (e.g., OutOfMemoryError), while exceptions are conditions that applications can handle (e.g., IOException).

Answer 60

The stack stores method call frames, including local variables and control flow, while the heap stores objects and their associated data. The stack is faster but has limited size, while the heap is larger but slower.

Answer 61

A constructor initializes a new object and has the same name as the class, while a method performs operations and has a name that is different from the class name.

Answer 62

Checked exceptions must be declared or handled, while unchecked exceptions (RuntimeException and its subclasses) do not need to be explicitly handled or declared.

Answer 63

Use a try-catch block to handle exceptions: java Copy code try { // Code that may throw an exception } catch (Exception e) { // Handle the exception }

Answer 64

Implicit casting automatically converts a smaller data type to a larger one. Explicit casting manually converts a larger data type to a smaller one.

Answer 65

Autoboxing is the automatic conversion of primitive types to their corresponding wrapper classes. Unboxing is the conversion of wrapper classes back to primitive types.

Answer 66

Operations on a List include adding, removing, and accessing elements, as well as sorting and iterating through the list.

Answer 67

Polymorphism allows objects to be treated as instances of their parent class, enabling one interface to be used for a general class of actions. Use it to simplify code and enhance flexibility.

Answer 68

Inheritance allows a class to inherit fields and methods from another class, promoting code reuse and creating a hierarchical relationship. Use it to extend functionality and create specialized subclasses.

Answer 69

Method overriding redefines a method in a subclass with the same signature as in the parent class. Method overloading involves defining multiple methods with the same name but different signatures in the same class.

Answer 70

Commonly overridden methods include toString(), equals(), and hashCode(). These methods provide custom string representations, equality checks, and hash codes for objects.

Answer 71

Define state and behavior specific to a subclass, such as unique attributes and methods that extend or refine the parent class functionality.

Answer 72

Define state and behavior in a parent class that is common to all subclasses, such as shared properties and methods that are not specific to any single subclass.

Answer 73

Upcasting refers to casting a subclass object to its superclass type. This is safe and allows for more general handling of objects.

Answer 74

Downcasting refers to casting a superclass object to a subclass type. This requires an explicit cast and should be done with caution to avoid ClassCastException.

Answer 75

A Collection is a framework in Java that provides a set of classes and interfaces for storing and manipulating groups of objects.

Answer 76

Stack: A collection that follows LIFO (Last-In-First-Out) order. Example operations include push and pop. Queue: A collection that follows FIFO (First-In-First-Out) order. Example operations include enqueue and dequeue.