Linux 命令行搭建Java环境

当Linux不启用图形界面的时候，我们只能通过命令行来搭建Java环境了。
平台： CentOS 6.5

1. 下载

不知道后续Oracle公司会不会会不会更新网址，所以以当前时间(2016年7月19日)为例。如果我们有浏览器，只需要输入以下网址：
http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html
就能打开Java jdk 的下载页面了。然后下载即可。
下载的时候需要点击“Accept License Agreement ”，所以用这个命令：

wget http://download.oracle.com/otn-pub/java/jdk/8u91-b14/jdk-8u91-linux-x64.tar.gz

下载下来的文件只有5K左右，只是一个一个HTML文件罢了。所以需要输入以下命令：

wget --no-check-certificate --no-cookies --header "Cookie: oraclelicense=accept-securebackup-cookie" http://download.oracle.com/otn-pub/java/jdk/8u91-b14/jdk-8u91-linux-x64.tar.gz

这样就能下载jdk-8u91-linux-x64.tar.gz 这个压缩包了。

2. 解压

建立一个目录，如我这里建的目录是/usr/java/jdk8。

mkdir /usr/javamkdir /usr/java/jdk8

利用以下命令解压刚才下载的jdk-8u91-linux-x64.tar.gz压缩包。进入这个压缩包所在的目录，然后输入以下命令：

tar zxvf jdk-8u91-linux-x64.tar.gz -C /usr/java/jdk8/

解压之后/usr/java/jdk8/目录下有一个目录：jdk1.8.0_91。这就是JDK的安装目录。

3. 设置环境变量

修改配置文件:

vim ~/.bashrc

在文件中加入：

export JAVA_HOME=/usr/java/jdk8/jdk1.8.0_91/export JRE_HOME=${JAVA_HOME}/jreexport CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/libexport PATH=${JAVA_HOME}/bin:$PATH

然后输入命令让配置文件生效：

source ~/.bashrc

4. 测试

可以输入java和javac这两个命令测试一下。
输入java输出结果：

Usage: java [-options] class [args...]           (to execute a class)   or  java [-options] -jar jarfile [args...]           (to execute a jar file)where options include:    -d32      use a 32-bit data model if available    -d64      use a 64-bit data model if available    -server   to select the "server" VM                  The default VM is server.    -cp <class search path of directories and zip/jar files>    -classpath <class search path of directories and zip/jar files>                  A : separated list of directories, JAR archives,                  and ZIP archives to search for class files.    -D<name>=<value>                  set a system property    -verbose:[class|gc|jni]                  enable verbose output    -version      print product version and exit    -version:<value>                  Warning: this feature is deprecated and will be removed                  in a future release.                  require the specified version to run    -showversion  print product version and continue    -jre-restrict-search | -no-jre-restrict-search                  Warning: this feature is deprecated and will be removed                  in a future release.                  include/exclude user private JREs in the version search    -? -help      print this help message    -X            print help on non-standard options    -ea[:<packagename>...|:<classname>]    -enableassertions[:<packagename>...|:<classname>]                  enable assertions with specified granularity    -da[:<packagename>...|:<classname>]    -disableassertions[:<packagename>...|:<classname>]                  disable assertions with specified granularity    -esa | -enablesystemassertions                  enable system assertions    -dsa | -disablesystemassertions                  disable system assertions    -agentlib:<libname>[=<options>]                  load native agent library <libname>, e.g. -agentlib:hprof                  see also, -agentlib:jdwp=help and -agentlib:hprof=help    -agentpath:<pathname>[=<options>]                  load native agent library by full pathname    -javaagent:<jarpath>[=<options>]                  load Java programming language agent, see java.lang.instrument    -splash:<imagepath>                  show splash screen with specified imageSee http://www.oracle.com/technetwork/java/javase/documentation/index.html for more details.

输入javac 的输出结果：

Usage: javac <options> <source files>where possible options include:  -g                         Generate all debugging info  -g:none                    Generate no debugging info  -g:{lines,vars,source}     Generate only some debugging info  -nowarn                    Generate no warnings  -verbose                   Output messages about what the compiler is doing  -deprecation               Output source locations where deprecated APIs are used  -classpath <path>          Specify where to find user class files and annotation processors  -cp <path>                 Specify where to find user class files and annotation processors  -sourcepath <path>         Specify where to find input source files  -bootclasspath <path>      Override location of bootstrap class files  -extdirs <dirs>            Override location of installed extensions  -endorseddirs <dirs>       Override location of endorsed standards path  -proc:{none,only}          Control whether annotation processing and/or compilation is done.  -processor <class1>[,<class2>,<class3>...] Names of the annotation processors to run; bypasses default discovery process  -processorpath <path>      Specify where to find annotation processors  -parameters                Generate metadata for reflection on method parameters  -d <directory>             Specify where to place generated class files  -s <directory>             Specify where to place generated source files  -h <directory>             Specify where to place generated native header files  -implicit:{none,class}     Specify whether or not to generate class files for implicitly referenced files  -encoding <encoding>       Specify character encoding used by source files  -source <release>          Provide source compatibility with specified release  -target <release>          Generate class files for specific VM version  -profile <profile>         Check that API used is available in the specified profile  -version                   Version information  -help                      Print a synopsis of standard options  -Akey[=value]              Options to pass to annotation processors  -X                         Print a synopsis of nonstandard options  -J<flag>                   Pass <flag> directly to the runtime system  -Werror                    Terminate compilation if warnings occur  @<filename>                Read options and filenames from file</span>

那就说明Java环境已经搭建好了。