Java Basic Concepts

API

Application Programme Interface → application interface. The main feature of Java is its object-oriented oo → Object Oriented → object-oriented. Therefore, many basic application interfaces (APIS) are set. Do you commonly use import when designing programs !? That is, the method to reference the API.

 

J2sdk

J2sdk = JDK + JRE, j2sdk (Java 2 software development kit) → Java2 software development kit, including the Java compiler and Java virtual appliance.

 

JDK

Java Development Kit → Java Development Kit, sometimes referred to as j2sdk.

Let's talk about this topic. Since Java was upgraded from version 1.1 to version 1.2, it has changed a lot. to distinguish it from previous versions, all versions after version 1.2 are collectively referred to as Java2.
JDK is the core of Java, including the Java Runtime Environment JRE (Java Runtime Environment), a bunch of Java tools and Basic Java class libraries. No matter what Java application server is actually built into a certain version of JDK. Therefore, mastering JDK is the first step to learn java well.

The most popular JDK is the JDK released by Sun. In addition to sun, many companies and organizations have developed their own JDK, such as JDK developed by IBM and jrocket of Bea, and JDK developed by GNU. Among them, the JVM (Java Virtual Machine) Running Efficiency of ibm jdk is much higher than that of Sun JDK. The jrocket running on the X86 platform is much more efficient on the server than Sun JDK.

Jdk1.4.2: http://java.sun.com/j2se/1.4.2/download.html

 

JVM

Java Virtual Machine → Java virtual machine, which translates Java bytecode into a language that the computer's CPU can understand. Java has designed a virtual machine to implement the platform independence function, which makes Java highly portable.

 

JRE

Java Runtime Environment → Java Runtime Environment. Is the JVM program implementation. With this, you can run Java programs.

 

Here we will explain the Java structure in graphical form.

The image of this topic is as follows: