JDK manufacturer open source JDK OpenJDK JDK installation Java installation JDK version difference difference between Java versions Java8 to Java17 changes jdk8 to jdk17 changes

1. JDK manufacturer

• Oracle JDK Official
• OpenJDK open source
• Amazon Corretto JDK Open Source
• AdoptOpenJDK open source
• Azul Zulu: Azul Systems Free
• Red Hat OpenJDK
• IBM JDK
• SAP Machine JDK Open Source

2. JDK installation (example is JDK 8)

Official installation documentation

https://docs.oracle.com/javase/8/docs/technotes/guides/install/windows_jdk_install.html#CHDEBCCJ

2.1. Download the JDK8 installation package

Download address , Oracle official website JDK requires login

Choose to download according to your computer system

If you don’t have an account, you can use the JDK8 installation package I downloaded ( 包含中文文档) 123 network disk. You don’t need to log in to download the network disk.

Double-click the jdk installer to install.

Select all three packages to install.

Just keep clicking next step.

2.2. Environment variable configuration

2.2.1. Configure JAVA_HOME environment variable

Open environment variable settings > Create new environment variable JAVA_HOME

Variable name: JAVA_HOME
Variable value:jdk安装目录; 变量值是自己的jdk安装目录：例如：D:\JDK\jdk1.8.0_161

2.2.2. Configure CLASSPATH environment variable

Open environment variable settings > Create new environment variable CLASSPATH

Variable name: CLASSPATH
Variable value:.;%JAVA_HOME%\lib\dt.jar;%JAVA_HOME%\lib\tools.jar

2.2.3. Configure Path environment variable

Open the environment variable settings > find Pathand edit this environment variable

Create a new environment variable value.
Variable value: %JAVA_HOME%\bin

Pay special attention here. The win10 environment variable value is a whole line, not line by line like Win11. The added Pathvariable value in win10 %JAVA_HOME%\bin;has an extra ;trailing semicolon .

Finally test whether the installation is successful

Open CMD and run. java -versionIf the version number appears, the installation is successful.

3. Changes from Java8 to Java17

JDK 8:

Main upgrade contents:

• Lambda expression: supports functional programming.
• Functional interface: Introduction of Function, Predicate, Consumer and other interfaces.
• Stream: Functional streaming operations for processing collection data.
• New date and time API: The java.time package is introduced to provide better date and time processing.
• Default methods: Allows defining default implementations in interfaces.
• New garbage collector: such as G1 collector, etc.
• Nashorn JavaScript engine: used to run JavaScript code in Java.

Content removed:

• PermGen and associated garbage collectors: replaced by Metaspace.

JDK 9:

Main upgrade contents:

• Modular system (Jigsaw project): The concept of modularity is introduced and a module system is added.
• Interface private methods: Allows defining private methods in the interface.
• Improved Javadoc: The Javadoc tool has been improved to provide a better documentation generation experience.
• New garbage collector: such as G1 collector, etc.

JDK 10:

Main upgrade contents:

• Local variable type inference: Allows the use of the var keyword in the declaration of local variables for type inference.
• Parallel full garbage collector: Improved performance of parallel GC.
• Application Class Data Sharing: Improves the speed of application startup.

JDK 11:

Main upgrade contents:

• HTTP client standard API: The standard HTTP client API is introduced.
• Local variable syntax enhancement: allows the use of the var keyword in Lambda expressions for type inference.
• Nested Access Control: Added some new access control modifiers.
• ZGC Garbage Collector: Introduces a low-latency garbage collector.

JDK 12:

Main upgrade contents:

• Switch expression: Enhanced the writing method of Switch statement.
• New garbage collector (Shenandoah collector): A low-latency garbage collector is introduced.

JDK 13:

Main upgrade contents:

• Text Blocks: Simplifies the way to write multi-line strings.
• Switch expression improvements: The functionality of Switch expressions has been further enhanced.
• Dynamic CDS (Class Data Sharing): Improves the speed of application startup.

JDK 14:

Main upgrade contents:

• JEP343 (Garbage Collector Interface): Defines the interface of the garbage collector.
• JEP345 (Prophet): Used to predict future data based on historical data.
• JEP359 (Record Types): Introduces a new data type for quickly defining immutable data classes.

JDK 15:

Main upgrade contents:

• Hidden Classes: Used to improve the performance of dynamic languages.
• Sealed Classes: Restrict class inheritance.
• GC's Epsilon collector: a no-op garbage collector.

JDK 16:

Main upgrade contents:

• Record types (Records): Simplified the definition of data classes.
• Pattern Matching: Enhanced pattern matching function of Switch expression.
• Garbage Collector (ZGC, Shenandoah): Improved garbage collector performance and efficiency.

JDK 17:

Main upgrade contents:

• Sealed Classes: Enhanced the flexibility of Sealed Classes.
• Pattern Matching: Pattern matching functionality has been further improved.
• Garbage Collector (ZGC, Shenandoah): Further improvements to the performance and efficiency of the garbage collector.