Redhat Enterprise 5 中自带安装了jdk1.4，在安装jdk1.6前，把jdk1.4卸载：
1. 首先查看系统自带的JDK版本：
[root@linux ~]# java -version java version "1.4.2" gij (GNU libgcj) version 4.1.2 20080704 (Red Hat 4.1.2-48) Copyright (C) 2006 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
2. 确定JDK的具体版本号，然后将其卸载：
[root@linux ~]# rpm -qa | grep jdk [root@linux ~]# rpm -qa | grep gcj libgcj-4.1.2-42.el5 java-1.4.2-gcj-compat-1.4.2.0-40jpp.115
上面先确认jdk的具体版本号，然后使用rpm -e --nodeps命令删除上面查找的内容：
#rpm -e --nodeps java-1.4.2-gcj-compat-1.4.2.0-40jpp.115 Complete!
3. 再次检查JDK版本，卸载成功:
[root@linux ~]# java -version -bash: ./usr/bin/java: No such file or directory
二、jdk1.6安装
下面开始手动安装the latest jdk1.6 version，jdk-6u33-linux-i586.bin
1. 给jdk-6u33-linux-i586.bin分配权限，具体的这里要给它可执行的权限
[root@linux ~]# chmod +x jdk-6u33-linux-i586.bin
2. 然后解压：./jdk-6u33-linux-i586.bin
[root@linux ~]# ./jdk-6u33-linux-i586.bin
3. 执行之后会有一堆agreement什么的，一路more下去。接着有个确认安装的，输入yes，然后回车。开始解压。一直到
Java(TM) SE Development Kit 6 successfully installed.
.........
Press Enter to continue.....
Done.
4. 解压后的文件如下所示：
[root@linux ~]# ls
jdk1.6.0_33 jdk-6u33-linux-i586.bin
5. 一般都将安装文件放在usr/local下，执行拷贝：
[root@linux ~]# mv jdk1.6.0_33 /usr/local [root@linux ~]# cd /usr/local [root@linux local]# ls bin etc games include jdk1.6.0_33 lib libexec sbin share src
6. jdk已经成功搬运到了/usr/local下，然后就是最后一步，设置环境变量了。
7. 这里有两种设置，一种是通过export设置临时生效，重启之后设置会丢失，一种是将设置写入/etc/profile文件中，可以一直生效。所以，最好的设置当然是写入文件中了。先执行下面命令：
[root@linux local]# vi /etc/profile
8. 打开profile文件后输入i进入insert模式，在文件最后面添加如下内容。
export JAVA_HOME="/usr/local/jdk1.6.0_33"
export CLASS_PATH="$JAVA_HOME/lib:$JAVA_HOME/jre/lib"
export PATH=".:$PATH:$JAVA_HOME/bin"
然后esc，输入:wq,保存退出。
9. 然后需要设置让更改生效：
[root@linux local]# source /etc/profile
当然，如果你喜欢重启的话，你reboot也可以。
10. 查看当前jdk版本。
[root@linux local]# java -version java version "1.6.0_33" Java(TM) SE Runtime Environment (build 1.6.0_33-b03) Java HotSpot(TM) Client VM (build 20.8-b03, mixed mode, sharing)
安装完毕！
==========================================================
另一种方法：
[root@localhost ~]# yum remove java Loaded plugins: rhnplugin, security This system is not registered with RHN. RHN support will be disabled. Setting up Remove Process Resolving Dependencies --> Running transaction check ---> Package java-1.4.2-gcj-compat.i386 0:1.4.2.0-40jpp.115 set to be erased --> Processing Dependency: java-gcj-compat for package: antlr --> Processing Dependency: java-gcj-compat for package: antlr --> Processing Dependency: java-gcj-compat >= 1.0.64 for package: gjdoc --> Processing Dependency: java-gcj-compat >= 1.0.64 for package: gjdoc --> Running transaction check ---> Package antlr.i386 0:2.7.6-4jpp.2 set to be erased ---> Package gjdoc.i386 0:0.7.7-12.el5 set to be erased --> Finished Dependency Resolution Dependencies Resolved ==================================================================================================================================== Package Arch Version Repository Size ==================================================================================================================================== Removing: java-1.4.2-gcj-compat i386 1.4.2.0-40jpp.115 installed 441 Removing for dependencies: antlr i386 2.7.6-4jpp.2 installed 2.5 M gjdoc i386 0.7.7-12.el5 installed 1.7 M Transaction Summary ==================================================================================================================================== Remove 3 Package(s) Reinstall 0 Package(s) Downgrade 0 Package(s) Is this ok [y/N]: y Downloading Packages: Running rpm_check_debug Running Transaction Test Finished Transaction Test Transaction Test Succeeded Running Transaction Erasing : antlr 1/3 Erasing : gjdoc 2/3 Erasing : java-1.4.2-gcj-compat 3/3 Removed: java-1.4.2-gcj-compat.i386 0:1.4.2.0-40jpp.115 Dependency Removed: antlr.i386 0:2.7.6-4jpp.2 gjdoc.i386 0:0.7.7-12.el5 Complete!