方法一：手动解压JDK的压缩包，然后设置环境变量
方法二：用yum安装JDK
方法三：用rpm安装JDK
方法四：Ubuntu 上使用apt-get安装JDK
1.在/usr/目录下创建java目录
[root@localhost~]#mkdir/usr/java [root@localhost~]#cd/usr/java
2.下载，然后解压
[root@localhostjava]#curl-Ohttp://download.oracle.com/otn-pub/java/jdk/7u79-b15/jdk-7u79-linux-x64.tar.gz [root@localhostjava]#tar-zxvfjdk-7u79-linux-x64.tar.gz
3.设置环境变量
[root@localhostjava]#vi/etc/profile
#setjavaenvironment 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 exportJAVA_HOMEJRE_HOMECLASS_PATHPATH
让修改生效：
[root@localhostjava]#source/etc/profile
4.验证
[root@localhostjava]#java-version javaversion"1.7.0_79" Java(TM)SERuntimeEnvironment(build1.7.0_79-b15) JavaHotSpot(TM)64-BitServerVM(build24.79-b02,mixedmode)
方法二：用yum安装JDK(CentOS)
1.查看yum库中都有哪些jdk版本
[root@localhost~]#yumsearchjava|grepjdk ldapjdk-javadoc.x86_64:Javadocforldapjdk java-1.6.0-openjdk.x86_64:OpenJDKRuntimeEnvironment java-1.6.0-openjdk-demo.x86_64:OpenJDKDemos java-1.6.0-openjdk-devel.x86_64:OpenJDKDevelopmentEnvironment java-1.6.0-openjdk-javadoc.x86_64:OpenJDKAPIDocumentation java-1.6.0-openjdk-src.x86_64:OpenJDKSourceBundle java-1.7.0-openjdk.x86_64:OpenJDKRuntimeEnvironment java-1.7.0-openjdk-demo.x86_64:OpenJDKDemos java-1.7.0-openjdk-devel.x86_64:OpenJDKDevelopmentEnvironment java-1.7.0-openjdk-javadoc.noarch:OpenJDKAPIDocumentation java-1.7.0-openjdk-src.x86_64:OpenJDKSourceBundle java-1.8.0-openjdk.x86_64:OpenJDKRuntimeEnvironment java-1.8.0-openjdk-demo.x86_64:OpenJDKDemos java-1.8.0-openjdk-devel.x86_64:OpenJDKDevelopmentEnvironment java-1.8.0-openjdk-headless.x86_64:OpenJDKRuntimeEnvironment java-1.8.0-openjdk-javadoc.noarch:OpenJDKAPIDocumentation java-1.8.0-openjdk-src.x86_64:OpenJDKSourceBundle ldapjdk.x86_64:TheMozillaLDAPJavaSDK
2.选择版本，进行安装
我们这里安装1.7版本
[root@localhost~]#yuminstalljava-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
[root@localhost~]#vi/etc/profile
#setjavaenvironment 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:$JRE_HOME/bin exportJAVA_HOMEJRE_HOMECLASS_PATHPATH
3.验证
同上。
注：因为采用yum安装jdk，系统考虑到多版本的问题，会用alternatives进行版本控制。开始，相应版本的jdk安装在/usr/lib/jvm/之后，会在alternatives中注册，在/etc/alternatives目录下会产生一些链接到/usr/lib/jvm/中刚安装好的jdk版本。
在/usr/bin下面会有链接到/etc/alternatives的相应的文件。比如，/usr/bin下面会有一个链接文件java的映射关系如下：
/usr/bin/java->/etc/alternatives/java /etc/alternatives/java->/usr/lib/jvm/jre-1.7.0-openjdk.x86_64/bin/java
这样，java命令不用设置环境变量，就可以正常运行了。但如果对于tomcat或其他软件来说还是要设置环境变量。
同样，如果安装新的版本jdk，就会重新链接到最新安装的jdk版本。当然，也可以使用alternatives修改所要使用的版本。
具体方法可参照：《使用Linux的alternatives管理多版本的软件》
1.下载
[hadoop@localhost~]$curl-Ohttp://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-ivhjdk-7u79-linux-x64.rpm Preparing...###########################################[100%] 1:jdk###########################################[100%] UnpackingJARfiles... rt.jar... jsse.jar... charsets.jar... tools.jar... localedata.jar... jfxrt.jar...
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@localhostbin]#ll|grepjava lrwxrwxrwx.1rootroot25Mar2811:24jar->/usr/java/default/bin/jar lrwxrwxrwx.1rootroot26Mar2811:24java->/usr/java/default/bin/java lrwxrwxrwx.1rootroot27Mar2811:24javac->/usr/java/default/bin/javac lrwxrwxrwx.1rootroot29Mar2811:24javadoc->/usr/java/default/bin/javadoc lrwxrwxrwx.1rootroot28Mar2811:24javaws->/usr/java/default/bin/javaws lrwxrwxrwx.1rootroot30Mar2811:24jcontrol->/usr/java/default/bin/jcontrol [root@localhostbin]#cd/usr/java/ [root@localhostjava]#ll total4 lrwxrwxrwx.1rootroot16Mar2811:24default->/usr/java/latest drwxr-xr-x.8rootroot4096Mar2811:24jdk1.7.0_79 lrwxrwxrwx.1rootroot21Mar2811:24latest->/usr/java/jdk1.7.0_79
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-cachesearchjava|grepjdk default-jdk-StandardJavaorJavacompatibleDevelopmentKit default-jdk-doc-StandardJavaorJavacompatibleDevelopmentKit(documentation) gcj-4.6-jdk-gcjandclasspathdevelopmenttoolsforJava(TM) gcj-jdk-gcjandclasspathdevelopmenttoolsforJava(TM) openjdk-6-dbg-JavaruntimebasedonOpenJDK(debuggingsymbols) openjdk-6-demo-JavaruntimebasedonOpenJDK(demosandexamples) openjdk-6-doc-OpenJDKDevelopmentKit(JDK)documentation openjdk-6-jdk-OpenJDKDevelopmentKit(JDK) openjdk-6-jre-lib-OpenJDKJavaruntime(architectureindependentlibraries) openjdk-6-source-OpenJDKDevelopmentKit(JDK)sourcefiles openjdk-7-dbg-JavaruntimebasedonOpenJDK(debuggingsymbols) openjdk-7-demo-JavaruntimebasedonOpenJDK(demosandexamples) openjdk-7-doc-OpenJDKDevelopmentKit(JDK)documentation openjdk-7-jdk-OpenJDKDevelopmentKit(JDK) openjdk-7-source-OpenJDKDevelopmentKit(JDK)sourcefiles uwsgi-plugin-jvm-openjdk-6-JavapluginforuWSGI(OpenJDK6) uwsgi-plugin-jwsgi-openjdk-6-JWSGIpluginforuWSGI(OpenJDK6) openjdk-6-jre-OpenJDKJavaruntime,usingHotspotJIT openjdk-6-jre-headless-OpenJDKJavaruntime,usingHotspotJIT(headless) openjdk-7-jre-OpenJDKJavaruntime,usingHotspotJIT openjdk-7-jre-headless-OpenJDKJavaruntime,usingHotspotJIT(headless) openjdk-7-jre-lib-OpenJDKJavaruntime(architectureindependentlibraries)
2.选择版本进行安装
root@Itble:~#apt-getinstallopenjdk-7-jdk
root@Itble:~#vi/etc/profile
#setjavaenvironment 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 exportJAVA_HOMEJRE_HOMECLASS_PATHPATH
root@Itble:~#source/etc/profile
root@Itble:~#java-version javaversion"1.7.0_79" OpenJDKRuntimeEnvironment(IcedTea2.5.5)(7u79-2.5.5-0ubuntu0.12.04.1) OpenJDK64-BitServerVM(build24.79-b02,63); line-height:30px"> Ubuntu的apt-get安装方式和CentOS的yum安装方式很类似，这里就不再啰嗦。
原文链接：https://www.f2er.com/centos/379706.html