1. 安装之前先测试现有JDK
$ java -version
java version “1.7.0_25”
OpenJDK Runtime Environment (fedora-2.3.10.4.fc19-i386)
OpenJDK Server VM (build 23.7-b01, mixed mode)
由此可以看出，默认为OpenJDK
2. 从官网下载Fedora的Oracle JDK。
http://www.oracle.com/technetwork/java/javase/downloads/index.html
对于Redhat系列可选用rpm的安装文件。比如：jdk-7u25-linux-i586.rpm 或者64位机的jdk-7u25-linux-x64.rpm。
3. 安装
rpm -ivh jdk-7u25-linux-i586.rpm
4. 配置环境变量
编辑/etc/profile, 在末尾加上：
#set java environment
JAVA_HOME=/usr/java/jdk1.7.0_25
CLASSPATH=.:$JAVA_HOME/lib/tools.jar:$JAVA_HOEM/lib/dt.jar
PATH=$JAVA_HOME/bin:$PATH
export JAVA_HOME CLASSPATH PATH
5. 安装设置SunJDK
$ sudo alternatives –install /usr/bin/java java /usrjava/jdk1.7.0_25/bin/java 500
$ sudo alternatives –install /usr/bin/javac javac /usr/java/jdk1.7.0_25/bin/javac 500
6.设置默认JDK
$ sudo alternatives –config java
There are 2 programs which provide ‘java’.
Selection Command
*+ 1 /usr/lib/jvm/jre-1.7.0-openjdk.i386/bin/java
2 /usr/java/jdk1.7.0_25/bin/java
Enter to keep the current selection[+], or type selection number: 2
当前默认为1序号的OpenJDK，所以选择2并设置SunJDK为默认。
再次通过命令确认：
$ sudo alternatives –config java
There are 2 programs which provide ‘java’.
Selection Command
- 1 /usr/lib/jvm/jre-1.7.0-openjdk.i386/bin/java
- 2 /usr/java/jdk1.7.0_25/bin/java
Enter to keep the current selection[+], or type selection number:
2序号的SunJDK已经被选为默认了。
7. 测试
$ java -version
java version “1.7.0_25”
Java(TM) SE Runtime Environment (build 1.7.0_25-b15)
Java HotSpot(TM) Server VM (build 23.25-b01, mixed mode)