Java (i)--Understanding the Java language

1. Introduction to the Java language

　Java is an object-oriented programming language that can compose cross-platform applications with exceptional versatility, efficiency, platform portability, and security. Sun's interpretation of the Java programming language is that the Java programming language is a simple, object-oriented, distributed, explanatory, robust, secure and system-independent, portable, high-performance, multithreaded , and dynamic language.

2. Three major systems of Java platform

Java is divided into three systems, namely Java SE(j2se,java2 Platform standard Edition, Standards Edition); Javaee(J2ee,java 2 Platform, Enterprise Edition, Corporate Edition) for building large enterprise applications or websites;Java ME(J2me,java 2 Platform micro Edition, mini version) for mobile terminals.

3. Java Development History

May 23, 1995, (born) Sun company launched, originally known as Oak, was 1991 for the embedded chip design, later renamed Java;

January 1996, the first jdk--jdk1.0 was born;

February 18, 1997, JDK1.1 released;

In June 1999, Sun released three versions of Java: Standard Edition, Enterprise Edition and mini Edition;

May 8, 2000, JDK1.3 released; May 29, JDK1.4 released;

April 20, 2009, Oracle acquires Sun and acquires Java copyright;

July 28, 2011, Oracle releases the official version of Java 7.0;

March 19, 2014, Oracle releases the official version of Java 8.0. In November, Oracle released the new features of Java 9.0

4. Core concept: JVM, JDK, JRE

Jvm:java Virtual machine (Java VM)

Jdk:java Development Kit (Java Development Kit)

Jre:java Runtime Environment (Java Runtime Environment)

　　

Relationship of three: JDK contains jre,jre containing JVM

　　

JVM Details:

Java source code is a. java file that is not executable and needs to be compiled into a platform-independent. Class bytecode file by the compiler and interpreted by the interpreter to execute, while the JVM includes compilers and interpreters. That is, the Java program requires the JVM to run.

JRE Details:

The JRE (Java Runtime Environment,java Runtime Environment) is the set of environments that the Java program must run, including the JVM standard implementation and the Java Core Class library, which can only be run by Java, not compiled, debugged, etc.

The JRE has a separate version, and if you only need to run Java programs, install the JRE.

　　

JDK Details:

The JDK (Java Development Kit,java Development Kit) is the Java Language Software Development Kit (SDK), a Java suite for Java developers.

The JDK includes the following basic components: compiler, jar packaging tool, Javadoc document generator, debug debugger, header file generator, disassembler, monitoring tool, etc.

The JDK contains the full JRE, and if the JDK is installed, the JRE is not installed because the JRE is integrated into the JDK.

　　　　

　

Java (i)--Understanding the Java language