我正在尝试在我的 ubuntu 上安装 openjdk-7,但出现以下错误:
$ sudo apt-get install openjdk-7-jre
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package openjdk-7-jre is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package openjdk-7-jre has no installation candidate
我想我错过了一些回购或类似的东西,但我无法找到任何参考地点和内容。