Before you learn Java

Java Basics

• Download JDK

JDK (Java Development Kit Java Development Kit)

Official website:

www.oracle.com See oracle.html

• installation Jdk

  　

  Fool-mounted, next.

  Recommendation: The installation path should not have Chinese or special symbols such as spaces.

  The JRE can choose not to install.

  　
  

  Specific steps:

  (1) Double-click jdk_1.8.0_32bit.exe to enter the following interface

  (2) Click "Next"

  This step has been configured to achieve The "JRE can choose not to install " purpose

  (3) Click "Next" to enter the installation interface

  after this step, the installation is complete.

(1) The javac.exe in the bin directory under the JDK installation directory is java 'sjava the language of the compiler ", by executing the program, generate the corresponding class type of file

(2) The Java.exe in the bin directory under the JDK installation directory is java 's "Start Java Virtual Machine program, by executing the program,the Java virtual machine loads The file of the appropriate class type and interprets the execution Java Program.

3 Configuring the environment variable path

look at the results :

Precautions:

The Eclipse and JDK version types remain consistent , either - bit

Path/classpath/java_home

1. PATHenvironment variables. The function is to specify the command search path,IThe command line executes commands such asJavaccompilingJavaprogram, it will go toPATHThe path specified by the variable to see if the appropriate command program can be found. We need to putJDKunder the installation directorybinThe directory is added to the existingPATHvariable,binThe directory contains frequently used executables such asJavac/java/javadocWait, set it up.PATHvariable, you can execute it in any directoryJavac/javaand other tools.

2. Classpath environment variable. The function is to specify the class search path, to use the class that has already been written, if you can, of course, find them, JVM classpth jdk installation directory of lib Dt.jar and tools.jar set to classpath

3. Java_home Environment variables. It points to the JDK's installation directory,eclipse/netbeans/tomcat and other software by searching java_home Variable to find and use the installed jdk.

The role and relationship of JDK,JRE,JVM
(1) function
JVM: Securing the Java language across platforms
Jre:java the operating environment of the program
Development environment of Jdk:java program
(2) Relationship
jdk:jre+ Tools
jre:jvm+ Class Library

Before you learn Java