Introduction to Java Programming

Study Notes

Introduction to Java

Java is a high-level, object-oriented programming language.
It is platform-independent, meaning Java code can run on any system with a Java Virtual Machine (JVM).
Java uses a bytecode intermediate language to achieve platform-independence.

JVM Architecture

The JVM is a virtual machine that executes Java bytecode.
It has a class loader, runtime data area, execution engine, and native interface.
The runtime data area includes a method area, heap, stack, and PC register.
The execution engine interprets or compiles bytecode into native machine code for execution.

Garbage Collection

Garbage collection is a crucial part of Java.
It automatically manages memory allocation and deallocation.
The JVM reclaims memory occupied by objects that are no longer referenced.
This improves memory management and reduces the risk of memory leaks.

Inner Classes

Inner classes are classes defined inside another class.
They can access the members of the outer class, even private members.
They can have different access modifiers (public, protected, private, etc.).
Inner classes can be static, allowing more flexibility and efficiency in code organization.

Wrapper Classes

Wrapper classes are used to convert primitive data types into objects.
These classes include Integer, Double, Boolean, etc.
They allow primitive values to be used in situations where only objects are allowed, such as as elements in collections.

String Classes

String classes in Java are immutable.
Once created, they cannot be changed.
String manipulation involves creating new String objects.
Methods like concat, substring, and replace return new String objects rather than modifying the original.

Interfaces

Interfaces define a set of abstract methods that classes must implement.
They enforce a common structure for related classes.
They promote abstraction and loose coupling.
Interfaces can contain constants or default methods.

Arrays

Arrays are used to store collections of elements of the same data type.
They are fixed-size data structures and elements are accessed by an index.
Java arrays provide a simple mechanism to handle collections of homogenous data.

Synchronization

Synchronization in Java ensures thread safety.
It prevents race conditions and ensures that multiple threads access shared resources correctly without conflicts.
Mechanisms for synchronization include synchronized keyword, ReentrantLock and Semaphore.

Lambda Expressions

Lambda expressions are short anonymous functions in Java.
They can provide conciseness and improve code readability in functional programming scenarios.
They are commonly used to pass functions or methods as an argument to other methods (or functions).

Packages

Packages organize Java classes into namespaces.
This prevents naming conflicts.
Packages help to manage and structure large Java programs.

Description

This quiz covers the fundamentals of Java programming, including its object-oriented nature and platform independence. Explore the architecture of the Java Virtual Machine, the importance of garbage collection, and the concept of inner classes. Test your knowledge of these essential Java concepts.