安装Java1.8

Downloading Latest Java Archive

Download latest Java SE Development Kit 8 release from its official download page or use following commands to download from shell.

For 64Bit

# cd /opt/
# wget --no-cookies --no-check-certificate --header "Cookie: gpw_e24=http%3A%2F%2F%2F; oraclelicense=accept-securebackup-cookie" "

# tar xzf jdk-8u45-linux-x64.tar.gz

For 32Bit

# cd /opt/
# wget --no-cookies --no-check-certificate --header "Cookie: gpw_e24=http%3A%2F%2F%2F; oraclelicense=accept-securebackup-cookie" "

# tar xzf jdk-8u45-linux-i586.tar.gz

Note: If Above wget command doesn’t not work for you watch this example video to download java source archive using terminal.

Install Java with Alternatives

After extracting archive file use alternatives command to install it. alternatives command is available in chkconfig package.

# cd /opt/jdk1.8.0_45/
# alternatives --install /usr/bin/java java /opt/jdk1.8.0_45/bin/java 2
# alternatives --config java


There are 3 programs which provide 'java'.

  Selection    Command
-----------------------------------------------
*  1           /opt/jdk1.7.0_71/bin/java
 + 2           /opt/jdk1.8.0_25/bin/java
   3           /opt/jdk1.8.0_45/bin/java

Enter to keep the current selection[+], or type selection number: 3 

At this point JAVA 8 has been successfully installed on your system. We also recommend to setup javac and jar commands path using alternatives

# alternatives --install /usr/bin/jar jar /opt/jdk1.8.0_45/bin/jar 2
# alternatives --install /usr/bin/javac javac /opt/jdk1.8.0_45/bin/javac 2
# alternatives --set jar /opt/jdk1.8.0_45/bin/jar
# alternatives --set javac /opt/jdk1.8.0_45/bin/javac 

Check Installed Java Version

Check the installed version of java using following command.

root@tecadmin ~# java -version


java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

Configuring Environment Variables

Most of java based application’s uses environment variables to work. Set the Java environment variables using following commands

• Setup JAVA_HOME Variable

# export JAVA_HOME=/opt/jdk1.8.0_45 

• Setup JRE_HOME Variable

# export JRE_HOME=/opt/jdk1.8.0_45/jre 

• Setup PATH Variable

# export PATH=$PATH:/opt/jdk1.8.0_45/bin:/opt/jdk1.8.0_45/jre/bin 

Also put all above environment variables in /etc/environment file for auto loading on system boot.
注意这一行：export PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin:/usr/local/src/jdk1.8.0_51/bin/:/usr/local/src/jdk1.8.0_51/jre/bin
不是单一的把上面一行复制进去就可以了。

补充：千万不要忘记编辑/etc/environment文件，因为重启变量就会失效。source  /etc/environment
补充几个命令：
查看当前变量的命令：env       set
重新加载环境变量文件的命令：source  /etc/environment