Configure JDK environment variables in Linux

I.Download JDK
1. log on to the Sun JDK official download URL: http://java.sun.com/javase/downloads/index.jsp
2. Download The jdk-1_5_0_07-linux-i586-rpm.bin File
 
Ii. Install JDK
1. Add executable permissions for jdk-1_5_0_07-linux-i586-rpm.bin files
# Root> chmod 755 jdk-1_5_0_07-linux-i586-rpm.bin
2. Perform jdk-1_5_0_07-linux-i586-rpm.bin
# Root>./jdk-1_5_0_07-linux-i586-rpm.bin
3. Install the PrM package file
# Root> rpm-IVH jdk-1_5_0_07-linux-i586.rpm

3. Configure the environment variables path, java_home, classpath, and jre_home.
Three environment variables are configured:
1. Modify the/etc/profile file (the system is valid)
(1) # root> VI/etc/profile
(2) Use the VI editor to add the following content before the profile file umask022 (behind done and before unset I:
Export java_home =/opt/jdk1.5 // JDK installation path
Export Path = $ java_home/bin: $ path
Export classpath =.: $ java_home/lib/dt. jar: $ java_home/lib/tools. Jar

Export jre_home = $ java_home/JRE

Make environment variables take effect: # source/etc/profile

Save and restart your computer

(3) log on again
[Note]
<1> use environment variables in Linux: separate paths, different from those in windows;
<2> in Linux, use ($ + environment variable name) to reference the original variable value. In Windows, use % + environment variable name + %. For example, $ path and % PATH %.
<3> no space exists in classpath. For example, c: \ Documents and Settings \ Seagar \ jdk1.5 in windows will be invalid path names.
<4> the current directory "." In classpath cannot be ignored.
<5> export exports environment variables as global variables
<6> case sensitivity

2. Modify the. bashrc file (valid for individual users)
(1) # root> VI/home/Seagar/. bashrc
(2) Use the VI editor to add the following statements to the. bashrc file:
Export java_home =/opt/jdk1.5 # JDK installation path
Export Path = $ java_home/bin: $ path
Export classpath =.: $ java_home/lib/dt. jar: java_home/lib/tools. Jar

Export jre_home = $ java_home/JRE
3. Modify it directly in Shell (the current shell is valid)
Export java_home =/opt/jdk1.5
Export Path = $ java_home/bin: $ path
Export classpath =. $ java_home/lib/dt. jar: java_home/lib/tools. Jar

4. Same as above

To enable JDK to be used by all users, you can:

VI/etc/profile. d/Java. Sh

Enter the following content in the new java. Sh file:

# Set Java environment

Java_home =/opt/jdk1.5

Classpath =.: $ java_home/lib/tools. Jar

Path = $ java_home/bin: $ path

Export java_home classpath path

Save and exit, and then assign the permission to Java. sh: chmod 755/etc/profile. d/Java. Sh

Run the echo command on the terminal to check the environment variable settings.

# Echo $ java_home

# Echo $ classpath

# Echo $ path

Iv. test installation
1. view the Java-version
2. Use the VI editor to compile a Java program
(1) # root> VI hello. Java
(2) Programming
Public class hello
{
Public static void main (string [] ARGs)
{
System. Out. println ("hello ");
}
}
3. Run the CD command to enter the hello. Java directory and enter javac hello. java.
4. Execute: Java hello

5. Output: Hello

5. Uninstall JDK

1. Uninstall the rpm jdk:

# Rpm-Qa | grep JDK

Show: jdk-1.6.0_10-fcs

This indicates that you have installed JDK and uninstalled it below,
Uninstall: # rpm-e -- nodeps jdk-1.6.0_22-fcs

2. Uninstall the built-in JDK version:
View the built-in JDK:
# Rpm-Qa | grep gcj
The following information is displayed:
Libgcj-4.1.2-44.el5
Java-1.4.2-gcj-compat-1.4.2.0-40jpp.115
Run the rpm-e -- nodeps command to delete the content found above:
# Rpm-e-nodeps java-1.4.2-gcj-compat-1.4.2.0-40jpp.115