1. 查询是否默认安装有JDK
  [root@localhost bin]# java -version
  java version "1.6.0_22"
  OpenJDK Runtime Environment (IcedTea6 1.10.4) (rhel-1.41.1.10.4.el6-x86_64)
  OpenJDK 64-Bit Server VM (build 20.0-b11, mixed mode)
  2. 删除默认的安装的OpenJdk
  [root@localhost bin]# rpm -qa | grep jdk
  java-1.6.0-openjdk-javadoc-1.6.0.0-1.41.1.10.4.el6.x86_64
  java-1.6.0-openjdk-1.6.0.0-1.41.1.10.4.el6.x86_64
  java-1.6.0-openjdk-devel-1.6.0.0-1.41.1.10.4.el6.x86_64
  [root@localhost bin]# rpm -e --nodeps java-1.6.0-openjdk-javadoc-1.6.0.0-1.41.1.10.4.el6.x86_64
  [root@localhost bin]# rpm -e --nodeps java-1.6.0-openjdk-1.6.0.0-1.41.1.10.4.el6.x86_64
  [root@localhost bin]# rpm -e --nodeps java-1.6.0-openjdk-devel-1.6.0.0-1.41.1.10.4.el6.x86_64
  [root@localhost bin]# rpm -qa | grep jdk
  [root@localhost bin]#
  3. Oracle官网下载
  自己去官网下
  jdk1.6.0_45-linux-x64.tar.gz
  4. 安装JDK
  [root@localhost soft]# tar -zxvf jdk1.6.0_45-linux-x64.tar.gz
  [root@localhost ~]# mkdir /usr/java
  [root@localhost ~]# mv jdk1.6.0_45/ /usr/java/jdk1.6.0_45
  5. 配置JDK环境变量
  配置/etc/profile,在文件末尾加上如下配置:
  JAVA_HOME=/usr/java/jdk1.6.0_45
  CLASSPATH=.:$JAVA_HOME/lib.tools.jar
  PATH=$JAVA_HOME/bin:$PATH
  export JAVA_HOME CLASSPATH PATH
  配置普通用户的.bash_profile,示例以crxj-app为例,则可 vi /home/crxj-app/.bash_profile,加上如下配置:
  JAVA_HOME=/usr/java/jdk1.6.0_45
  JAVA_BIN=/usr/java/jdk1.6.0_45/bin
  CLASSPATH=.:$JAVA_HOME/lib/tools.jar:$JAVA_HOME/lib:$JAVA_HOME/bin
  export JAVA_HOME JAVA_BIN CLASSPATH
  export PATH=$PATH:$JAVA_HOME/bin
  生效配置环境
  [crxj-app@CRXJ-APP-2 uap]$ source /etc/profile
  测试JDK环境
  #下列任意命令都可以检测JDK环境是否安装正确
  java -version
  javac -version
  echo $JAVA_HOME