CentOS JAVA安装及查看路径方法

一、安装：

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

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@linuxidc:~# 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@linuxidc:~# apt-get install openjdk-7-jdk

3.设置环境变量

root@linuxidc:~# vi /etc/profile

在打开的profile文件中添加如下内容

#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@linuxidc:~# source /etc/profile

4.验证(同上一方法)

二、查看安装路径：

总结一下如何查找JDK安装路径的方法

首先声明，echo $JAVA_HOME 方法是在已经配置了/etc/profile 文件的前提下查询的，如果该文件$JAVA_HOME配置错误，输出结果也是错误的。

其次，which java查询到的是java的执行路径，不是安装路径！！（以前我一直搞不清楚。。。面壁...）

再者，whereis java 也不能查询到安装路径，它就罗列出一堆包含java的文件，对查找安装路径一点用都没有！！！

最后，开始高潮部分：

如此寻找才能到达目的，100%！

另附上/etc/profile配置详细格式，

然后，source /etc/profile 使之立即生效。

 

 

javac: Command not found的解决办法：

在centos7的terminal中输入Java -verison是没问题的，但是javac的话就会提示没有此命令

百度了好久，说的很复杂，照着做了，最后也没有成功

后来在stackoverflow上看到了这个

84 down voteaccepted

You installed the JavaRuntime Environment (JRE) only, which does not contain javac. For javac, you have to install theOpenJDK Development Environment. You can install java-devel or java-1.6.0-openjdk-devel, which both includejavac. By the way: you can find out which package provides javac with a yum search, e.g. su -c 'yum provides javac' Another note: using yum and openjdk is only one possibility to install the JDK. Many people prefer Sun/Oracle's "original" SDK. See How to install Java SDK on CentOS? and links for alternatives.

大意就是我们用yum来装原生的就行了

使用

yum install java-devel

就行了