方法一：手动安装jdk的安装包，配置环境变量
1.在/usr/目录下创建java目录
[root@localhost ~]# mkdir/usr/java
[root@localhost ~]# cd /usr/java
2.下载安装包并解压
[root@localhost java]# curl -O http://download.oracle.com/otn-pub/java/jdk/7u79-b15/jdk-7u79-linux-x64.tar.gz [root@localhost java]# tar -zxvf jdk-7u79-linux-x64.tar.gz
3.设置环境变量
[root@localhost java]# vi /etc/profile
进入vi编辑模式，加入如下代码：
#set java environment JAVA_HOME=/usr/java/jdk1.7.0_79 JRE_HOME=/usr/java/jdk1.7.0_79/jre CLASS_PATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin export JAVA_HOME JRE_HOME CLASS_PATH PATH
让修改生效：
[root@localhost java]# source /etc/profile
4.验证
[root@localhost java]# java -version java version "1.7.0_79" Java(TM) SE Runtime Environment (build 1.7.0_79-b15) Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode)
方法二：用yum安装JDK(CentOS)
1.查看yum库中都有哪些jdk版本
[root@localhost ~]# yum search java|grep jdk ldapjdk-javadoc.x86_64 : Javadoc for ldapjdk java-1.6.0-openjdk.x86_64 : OpenJDK Runtime Environment java-1.6.0-openjdk-demo.x86_64 : OpenJDK Demos java-1.6.0-openjdk-devel.x86_64 : OpenJDK Development Environment java-1.6.0-openjdk-javadoc.x86_64 : OpenJDK API Documentation java-1.6.0-openjdk-src.x86_64 : OpenJDK Source Bundle java-1.7.0-openjdk.x86_64 : OpenJDK Runtime Environment java-1.7.0-openjdk-demo.x86_64 : OpenJDK Demos java-1.7.0-openjdk-devel.x86_64 : OpenJDK Development Environment java-1.7.0-openjdk-javadoc.noarch : OpenJDK API Documentation java-1.7.0-openjdk-src.x86_64 : OpenJDK Source Bundle java-1.8.0-openjdk.x86_64 : OpenJDK Runtime Environment java-1.8.0-openjdk-demo.x86_64 : OpenJDK Demos java-1.8.0-openjdk-devel.x86_64 : OpenJDK Development Environment java-1.8.0-openjdk-headless.x86_64 : OpenJDK Runtime Environment java-1.8.0-openjdk-javadoc.noarch : OpenJDK API Documentation java-1.8.0-openjdk-src.x86_64 : OpenJDK Source Bundle ldapjdk.x86_64 : The Mozilla LDAP Java SDK
2.选择版本，安装
[root@localhost ~]# yum install java-1.7.0-openjdk
注：默认的安装目录是在: /usr/lib/jvm/java-1.7.0-openjdk-1.7.0.75.x86_64
3.设置环境变量
[root@localhost ~]# vi /etc/profile
进入vi编辑模型，增加:
#set java environment JAVA_HOME=/usr/lib/jvm/java-1.7.0-openjdk-1.7.0.75.x86_64 JRE_HOME=$JAVA_HOME/jre CLASS_PATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin export JAVA_HOME JRE_HOME CLASS_PATH PATH
让修改生效：
[root@localhost java]# source /etc/profile
3.验证,同上
方法三：用rpm安装JDK
1.下载
[hadoop@localhost ~]$ curl -O http://download.oracle.com/otn-pub/java/jdk/7u79-b15/jdk-7u79-linux-x64.rpm
2.使用rpm命令安装
[root@localhost ~]# rpm -ivh jdk-7u79-linux-x64.rpm Preparing... ########################################### [100%] 1:jdk ###########################################[100%] Unpacking JAR files... rt.jar... jsse.jar... charsets.jar... tools.jar... localedata.jar... jfxrt.jar...
3.设置环境变量
[root@localhost java]# vi /etc/profile
进入VI编辑，添加：
#set java environment JAVA_HOME=/usr/java/jdk1.7.0_79 JRE_HOME=/usr/java/jdk1.7.0_79/jre CLASS_PATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin export JAVA_HOME JRE_HOME CLASS_PATH PATH
让修改生效：
[root@localhost java]# java -version java version "1.7.0_79" Java(TM) SE Runtime Environment (build 1.7.0_79-b15) Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode)
方法四：Ubuntu 上使用apt-get安装JDK
1.查看apt库都有哪些jdk版本
root@Itble:~# apt-cache search java|grep jdk default-jdk - Standard Java or Java compatible Development Kit default-jdk-doc - Standard Java or Java compatible Development Kit (documentation) gcj-4.6-jdk - gcj and classpath development tools for Java(TM) gcj-jdk - gcj and classpath development tools for Java(TM) openjdk-6-dbg - Java runtime based on OpenJDK (debugging symbols) openjdk-6-demo - Java runtime based on OpenJDK (demos and examples) openjdk-6-doc - OpenJDK Development Kit (JDK) documentation openjdk-6-jdk - OpenJDK Development Kit (JDK) openjdk-6-jre-lib - OpenJDK Java runtime (architecture independent libraries) openjdk-6-source - OpenJDK Development Kit (JDK) source files openjdk-7-dbg - Java runtime based on OpenJDK (debugging symbols) openjdk-7-demo - Java runtime based on OpenJDK (demos and examples) openjdk-7-doc - OpenJDK Development Kit (JDK) documentation openjdk-7-jdk - OpenJDK Development Kit (JDK) openjdk-7-source - OpenJDK Development Kit (JDK) source files uwsgi-plugin-jvm-openjdk-6 - Java plugin for uWSGI (OpenJDK 6) uwsgi-plugin-jwsgi-openjdk-6 - JWSGI plugin for uWSGI (OpenJDK 6) openjdk-6-jre - OpenJDK Java runtime, using Hotspot JIT openjdk-6-jre-headless - OpenJDK Java runtime, using Hotspot JIT (headless) openjdk-7-jre - OpenJDK Java runtime, using Hotspot JIT openjdk-7-jre-headless - OpenJDK Java runtime, using Hotspot JIT (headless) openjdk-7-jre-lib - OpenJDK Java runtime (architecture independent libraries)
2.选择版本进行安装
root@Itble:~# apt-get install openjdk-7-jdk
3.设置环境变量
root@Itble:~# vi /etc/profile
添加如下内容：
#set java environment JAVA_HOME=/usr/lib/jvm/java-1.7.0-openjdk-amd64 JRE_HOME=$JAVA_HOME/jre CLASS_PATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin export JAVA_HOME JRE_HOME CLASS_PATH PATH
让修改生效：
root@Itble:~# source /etc/profile
4.验证
root@Itble:~# java -version java version "1.7.0_79" OpenJDK Runtime Environment (IcedTea 2.5.5) (7u79-2.5.5-0ubuntu0.12.04.1) OpenJDK 64-Bit Server VM (build 24.79-b02, mixed mode)