About Me
Oracle Certified Professional Java SE 11 Developer
1 Java Fundamentals
1-1 Java Basics
1-1 1 Java Platform Overview
1-1 2 Java Development Environment
1-1 3 Java Program Structure
1-1 4 Java Virtual Machine (JVM)
1-1 5 Java Development Kit (JDK)
1-1 6 Java Runtime Environment (JRE)
1-2 Object-Oriented Programming (OOP) Concepts
1-2 1 Classes and Objects
1-2 2 Inheritance
1-2 3 Polymorphism
1-2 4 Encapsulation
1-2 5 Abstraction
1-2 6 Interfaces
1-2 7 Abstract Classes
1-3 Data Types and Variables
1-3 1 Primitive Data Types
1-3 2 Reference Data Types
1-3 3 Variable Declaration and Initialization
1-3 4 Type Conversion and Casting
1-3 5 Arrays
1-4 Control Flow
1-4 1 Conditional Statements (if, else, switch)
1-4 2 Looping Constructs (for, while, do-while)
1-4 3 Break and Continue Statements
1-4 4 Exception Handling
2 Java Collections Framework
2-1 Collections Overview
2-1 1 Collection Interfaces
2-1 2 Collection Classes
2-1 3 Collection Algorithms
2-2 Lists
2-2 1 ArrayList
2-2 2 LinkedList
2-2 3 List Operations
2-3 Sets
2-3 1 HashSet
2-3 2 TreeSet
2-3 3 LinkedHashSet
2-4 Maps
2-4 1 HashMap
2-4 2 TreeMap
2-4 3 LinkedHashMap
2-5 Queues and Deques
2-5 1 PriorityQueue
2-5 2 ArrayDeque
3 Java Streams and Lambda Expressions
3-1 Lambda Expressions
3-1 1 Lambda Syntax
3-1 2 Functional Interfaces
3-1 3 Method References
3-2 Streams
3-2 1 Stream Creation
3-2 2 Intermediate Operations
3-2 3 Terminal Operations
3-2 4 Parallel Streams
4 Java Concurrency
4-1 Threads
4-1 1 Thread Creation
4-1 2 Thread States
4-1 3 Thread Synchronization
4-1 4 Thread Communication
4-2 Concurrency Utilities
4-2 1 Executor Framework
4-2 2 Concurrent Collections
4-2 3 Atomic Variables
4-2 4 Locks
5 Java IO and NIO
5-1 Input and Output Streams
5-1 1 Byte Streams
5-1 2 Character Streams
5-1 3 Buffered Streams
5-2 File IO
5-2 1 File Class
5-2 2 FileReader and FileWriter
5-2 3 FileInputStream and FileOutputStream
5-3 NIO (New IO)
5-3 1 Path Interface
5-3 2 Files Class
5-3 3 Channels and Buffers
5-3 4 Asynchronous IO
6 Java Date and Time API
6-1 Date and Time Classes
6-1 1 LocalDate
6-1 2 LocalTime
6-1 3 LocalDateTime
6-1 4 ZonedDateTime
6-2 Period and Duration
6-2 1 Period Class
6-2 2 Duration Class
6-3 Time Zones and Calendars
6-3 1 TimeZone Class
6-3 2 Calendar Class
7 Java Modules
7-1 Module System Overview
7-1 1 Module Declaration
7-1 2 Module Path
7-1 3 Module Dependencies
7-2 Module Resolution
7-2 1 Automatic Modules
7-2 2 Named Modules
7-2 3 Unnamed Modules
7-3 Module Services
7-3 1 Service Provider Interface (SPI)
7-3 2 ServiceLoader Class
8 Java Security
8-1 Security Basics
8-1 1 Security Manager
8-1 2 Permissions
8-1 3 Policy Files
8-2 Cryptography
8-2 1 Key Generation
8-2 2 Encryption and Decryption
8-2 3 Digital Signatures
8-3 Secure Coding Practices
8-3 1 Input Validation
8-3 2 Secure Communication
8-3 3 Authentication and Authorization
9 Java Networking
9-1 Networking Basics
9-1 1 InetAddress Class
9-1 2 URL and URLConnection Classes
9-2 Sockets
9-2 1 Socket Class
9-2 2 ServerSocket Class
9-2 3 DatagramSocket Class
9-3 Networking Protocols
9-3 1 TCPIP
9-3 2 UDP
9-3 3 HTTP
10 Java Database Connectivity (JDBC)
10-1 JDBC Basics
10-1 1 JDBC Architecture
10-1 2 JDBC Drivers
10-1 3 Establishing a Connection
10-2 Executing SQL Statements
10-2 1 Statement Interface
10-2 2 PreparedStatement Interface
10-2 3 CallableStatement Interface
10-3 ResultSet
10-3 1 ResultSet Interface
10-3 2 ResultSetMetaData Interface
10-4 Transaction Management
10-4 1 Commit and Rollback
10-4 2 Savepoints
11 Java Annotations
11-1 Annotation Basics
11-1 1 Annotation Types
11-1 2 Meta-Annotations
11-1 3 Annotation Processing
11-2 Standard Annotations
11-2 1 @Override
11-2 2 @Deprecated
11-2 3 @SuppressWarnings
11-3 Custom Annotations
11-3 1 Annotation Creation
11-3 2 Annotation Usage
12 Java Reflection
12-1 Reflection Basics
12-1 1 Class Class
12-1 2 Field Class
12-1 3 Method Class
12-2 Dynamic Class Loading
12-2 1 ClassLoader Class
12-2 2 Dynamic Proxy
12-3 Reflection API
12-3 1 Accessing Class Members
12-3 2 Modifying Class Members
13 Java Internationalization (I18N)
13-1 I18N Basics
13-1 1 Locale Class
13-1 2 ResourceBundle Class
13-2 Formatting
13-2 1 NumberFormat Class
13-2 2 DateFormat Class
13-2 3 MessageFormat Class
13-3 Character Encoding
13-3 1 Charset Class
13-3 2 String Encoding and Decoding
14 Java Platform Module System (JPMS)
14-1 Module System Overview
14-1 1 Module Declaration
14-1 2 Module Path
14-1 3 Module Dependencies
14-2 Module Resolution
14-2 1 Automatic Modules
14-2 2 Named Modules
14-2 3 Unnamed Modules
14-3 Module Services
14-3 1 Service Provider Interface (SPI)
14-3 2 ServiceLoader Class
15 Java 11 New Features
15-1 New String Methods
15-1 1 isBlank()
15-1 2 lines()
15-1 3 repeat()
15-2 New File Methods
15-2 1 writeString()
15-2 2 readString()
15-3 Local-Variable Syntax for Lambda Parameters
15-3 1 var Keyword in Lambda Expressions
15-4 HTTP Client API
15-4 1 HttpClient Class
15-4 2 HttpRequest Class
15-4 3 HttpResponse Class
15-5 Nest-Based Access Control
15-5 1 Nest Host and Nest Members
15-5 2 Nest Access Control
15-6 Epsilon Garbage Collector
15-6 1 Epsilon GC Overview
15-6 2 Epsilon GC Use Cases
15-7 Flight Recorder
15-7 1 Flight Recorder Overview
15-7 2 Flight Recorder Use Cases
15-8 Application Class-Data Sharing (CDS)
15-8 1 CDS Overview
15-8 2 CDS Use Cases
15-9 Deprecations and Removals
15-9 1 Deprecated Features
15-9 2 Removed Features
1.1.5 Java Development Kit (JDK)

1.1.5 Java Development Kit (JDK)

The Java Development Kit (JDK) is a comprehensive software development environment used for developing Java applications. It includes the Java Runtime Environment (JRE), the Java compiler (javac), and various tools necessary for writing, testing, and debugging Java code.

Key Concepts

1. Java Runtime Environment (JRE)

The JRE is a subset of the JDK and provides the minimum runtime requirements to execute Java applications. It includes the Java Virtual Machine (JVM), core classes, and supporting files. The JRE is essential for running Java applications but does not include the tools needed for development.

2. Java Compiler (javac)

The Java compiler, javac, translates Java source code (.java files) into bytecode (.class files). This bytecode is then executed by the JVM. The compiler ensures that the code adheres to Java syntax and semantics, catching errors before the code is run.

3. Java Virtual Machine (JVM)

The JVM is the runtime engine that executes Java bytecode. It abstracts the underlying hardware and operating system, ensuring that Java applications run consistently across different platforms. The JVM is responsible for memory management, garbage collection, and providing a runtime environment for Java applications.

4. Development Tools

The JDK includes various development tools such as javadoc for generating documentation, jdb for debugging, and jar for packaging Java applications into a single archive. These tools enhance the development process by providing additional functionalities beyond just compiling and running code.

Examples and Analogies

JRE Example

Imagine you have a Java application that you want to run on your computer. You need the JRE to execute this application. Without the JRE, your computer would not have the necessary components to run the Java bytecode.

Java Compiler Example

Consider writing a Java program to calculate the area of a circle. You would write the source code in a .java file and use the javac compiler to translate this code into bytecode. This bytecode can then be executed by the JVM.

JVM Example

Think of the JVM as a universal translator. If you have a Java program that needs to run on both Windows and Linux, the JVM translates the bytecode into a format that each operating system can understand. This ensures that your program runs smoothly on both platforms.

Development Tools Example

Suppose you want to generate documentation for your Java project. You can use the javadoc tool to automatically create HTML pages documenting your code. This is similar to using a word processor to create a user manual for a product.

By understanding these key concepts and their practical applications, you will be well-equipped to utilize the JDK effectively in your Java development journey.

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