CentOS下安装JDK的三种方法

方法一：手动解压JDK的压缩包，然后设置环境变量

1.在/usr/目录下创建java目录

[root@localhost ~]# mkdir/usr/java
[root@localhost ~]# cd /usr/java

2.下载jdk,然后解压

[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

在profile中添加如下内容:

#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JDK有效性

[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

1.查看yum库中都有哪些jdk版本(暂时只发现了openjdk)

[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,进行安装

//选择1.7版本进行安装

[root@localhost ~]# yum install java-1.7.0-openjdk

//安装完之后，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

在profile文件中添加如下内容

#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

4.验证(同上一方法)

方法三：用rpm安装JDK

1.下载rpm安装文件

[root@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

3.设置环境变量

[root@localhost java]# vi /etc/profile

在打开的profile文件中添加如下内容

#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(同上一方法)

注:和yum安装类似，不用设置环境变量就可以运行java命令。rpm安装方式默认会把jdk安装到/usr/java/jdk1.7.0_79，然后通过三层链接，链接到/usr/bin,具体链接如下：

[root@localhost ~]# cd /bin
[root@localhost bin]# ll|grep java
lrwxrwxrwx. 1 root root    25 Mar 28 11:24 jar ->/usr/java/default/bin/jar
lrwxrwxrwx. 1 root root    26 Mar 28 11:24 java -> /usr/java/default/bin/java
lrwxrwxrwx. 1 root root    27 Mar 28 11:24 javac ->/usr/java/default/bin/javac
lrwxrwxrwx. 1 root root    29 Mar 28 11:24 javadoc ->/usr/java/default/bin/javadoc
lrwxrwxrwx. 1 root root    28 Mar 28 11:24 javaws ->/usr/java/default/bin/javaws
lrwxrwxrwx. 1 root root    30 Mar 28 11:24 jcontrol ->/usr/java/default/bin/jcontrol
[root@localhost bin]# cd /usr/java/
[root@localhost java]# ll
total 4
lrwxrwxrwx. 1 root root  16 Mar 28 11:24 default-> /usr/java/latest
drwxr-xr-x. 8 root root 4096 Mar 28 11:24 jdk1.7.0_79
lrwxrwxrwx. 1 root root  21 Mar 28 11:24 latest -> /usr/java/jdk1.7.0_79