Java安装

下载

官网地址:Java Linux

wget下载

直接复制下载地址然后使用wget下载会出错,参考:如何用wget下载jdk

wget --no-check-certificate --no-cookies --header "Cookie: oraclelicense=accept-securebackup-cookie" + 右键复制的链接

设置环境变量

参考:ubuntu18.04 安装java

修改文件/etc/profile,添加如下环境变量

$ sudo vim /etc/profile
# JAVA
export JAVA_HOME=/home/zj/software/java/jdk1.8.0_201
export JRE_HOME=$JAVA_HOME/jre
export CLASSPATH=.:$JAVA_HOME/lib:$JRE_HOME/lib:$CLASSPATH
export PATH=$JAVA_HOME/bin:$JRE_HOME/bin:$PATH

重启即可

修改系统默认JDK

参考:Ubuntu18.04安装和配置 Java JDK 和 JRE,并卸载自带OpenJDK

系统默认安装了OpenJDK,可以设置成SunJDK

首先添加SunJDK命令到update-alternatives

$ sudo update-alternatives --install /usr/bin/java java /home/zj/software/java/jdk1.8.0_201/bin/java 300

$ sudo update-alternatives --install /usr/bin/javac javac /home/zj/software/java/jdk1.8.0_201/bin/javac 300
update-alternatives: using /home/zj/software/java/jdk1.8.0_201/bin/javac to provide /usr/bin/javac (javac) in auto mode

$ sudo update-alternatives --install /usr/bin/jar jar /home/zj/software/java/jdk1.8.0_201/bin/jar 300
update-alternatives: using /home/zj/software/java/jdk1.8.0_201/bin/jar to provide /usr/bin/jar (jar) in auto mode

$ sudo update-alternatives --install /usr/bin/javah javah /home/zj/software/java/jdk1.8.0_201/bin/javah 300
update-alternatives: using /home/zj/software/java/jdk1.8.0_201/bin/javah to provide /usr/bin/javah (javah) in auto mode

$ sudo update-alternatives --install /usr/bin/javp javap /home/zj/software/java/jdk1.8.0_201/bin/javap 300
update-alternatives: using /home/zj/software/java/jdk1.8.0_201/bin/javap to provide /usr/bin/javp (javap) in auto mode

添加了java/javac/jar/javah/javap,有些是系统没有配置的,比如javac/jar/javah/javap,有些是系统已有配置的,比如java

然后设置SunJDK命令为指定配置

$ sudo update-alternatives --config java
There are 2 choices for the alternative java (providing /usr/bin/java).

Selection    Path                                            Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      auto mode
1            /home/zj/software/java/jdk1.8.0_201/bin/java     300       manual mode
2            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      manual mode

Press <enter> to keep the current choice[*], or type selection number: 1   
update-alternatives: using /home/zj/software/java/jdk1.8.0_201/bin/java to provide /usr/bin/java (java) in manual mode

$ sudo update-alternatives --config javac
There is only one alternative in link group javac (providing /usr/bin/javac): /home/zj/software/java/jdk1.8.0_201/bin/javac
Nothing to configure.

测试

$ java -version
java version "1.8.0_201"
Java(TM) SE Runtime Environment (build 1.8.0_201-b09)
Java HotSpot(TM) 64-Bit Server VM (build 25.201-b09, mixed mode)
$ javac -version
javac 1.8.0_201