程序 'java' 已包含在下列软件包中：
* default-jre
* gcj-4.8-jre-headless
* openjdk-7-jre-headless
* gcj-4.6-jre-headless
* openjdk-6-jre-headless
请尝试：apt-get install <选定的软件包>
sudo update-alternatives –install /usr/bin/javac javac /home/java/jdk1.8.0_191/bin/java 300
sudo update-alternatives --install /usr/bin/javac javac /home/java/jdk1.8.0_191/bin/javac 300