Java - Intermediate Flashcards
1
Q
JDK
A
JDK (Java Development Kit) is a software development environment that provides tools and libraries necessary for developing Java applications.
It includes the:
1. compiler,
2. debugger,
4. and other development utilities.
2
Q
JRE
A
- JRE (Java Runtime Environment)
- is an implementation of the JVM (Java Virtual Machine)
- along with libraries and other files required to run Java applications.
3
Q
JVM
A
- JVM (Java Virtual Machine)
- an abstract computing machine that executes Java bytecode.
- provides a runtime environment for Java applications (to run independently of the underlying hardware and operating system.)
4
Q
Explain the concept of polymorphism in Java
A
- it allows a subclass to override a method of its superclass, providing its own implementation.
- Polymorphism enables:
- code flexibility
- and reusability.
For Example:
class Shape {
void draw() {
System.out.println("Drawing a shape");
}
}
class Circle extends Shape {
@Override
void draw() {
System.out.println("Drawing a circle");
}
}
class Rectangle extends Shape {
@Override
void draw() {
System.out.println("Drawing a rectangle");
}
}
public class Main {
public static void main(String[] args) {
Shape circle = new Circle();
Shape rectangle = new Rectangle();
circle.draw(); // Output: Drawing a circle
rectangle.draw(); // Output: Drawing a rectangle
}
}
5
Q
What are the different types of collections available in Java?
A
- List
- Set
- Map
- Queue
6
Q
List
A
- Ordered
- Allows duplicates
- Example:
- ArrayList,
- LinkedList
7
Q
Set
A
- Unordered
- Does not allow duplicates
- Example:- HashSet
- TreeSet
8
Q
Map
A
- An interface for a collection that stores data in key value pairs
- The way it orders depends on the implementation type:
- HashMap doesn’t guarantee order
- TreeMap sorts based on natural order of the keys
- Example:
- HashMap,
- TreeMap,
- LinkedHashMap,
- ConcurrentHashMap
9
Q
Queue
A
Follows the FIFO (First-In-First-Out) principle.
10
Q
Explain the concept of generics in Java
A
- Generics allow the use of type parameters to create generic classes and methods.
- provide compile-time type checking, ensuring that the correct types are used at compile time and preventing type-related errors at runtime
11
Q
What are the benefits of Generics?
A
- compile-time type safety,
- and thus preventing type-related errors at runtime
12
Q
ArrayList
A
ArrayList is the List implemented for a resizable array.
- Dynamic Size
- Can access elements by index
- Ordered
- Duplicates allowed
- Null elements allowed
- Resizes by a factor of 1.5 or 2
13
Q
LinkedList
A
- double linked - knows prev and next node
- dynamically sized
- ordered
- duplicates allowed
- nulls allowed
Sequential access (walking the list) is better than random access.
14
Q
When should you use an ArrayList?
A
- When you need fast access to elements by index
- and when the list size doesn’t change frequently.
15
Q
When should you use LinkedLists?
A
- When you need to add or remove an element from the beginning or end,
- When you don’t know the size of the list you’re going to be working with.
- When you will be frequently adding or removing elements from the list. (ArrayLists have to shift each element forward or backward in the list whereas a linked list only has to update it’s prev/next pointers).
