Question

我有一台ubuntu机器，我安装了一个jdk版本。接下来我下载了第二个版本/ usr / local

现在，我想对/ usr / local中的第二个jdk运行一个程序，即我将在/ usr / local / bin中复制一个示例.java程序，然后执行。

但问题是，即使我导航到/ usr / local / bin并输入$ java -version 我正在获得首先安装的那个。对此有何解决方案？

Answer 1

输入sudo update-alternatives --config java

选择所需的版本。

我认为这个问题应该转移到askubuntu

Answer 2

当您运行java时没有路径时，您的shell会在$PATH环境变量中查找java。如果您需要特定的java，则需要更改$PATH，或使用路径运行它，例如：

/usr/local/bin/java

或者如果您真的想先cd，那么您可以运行

./java

来自/usr/local/bin

Answer 3

以下是在 Ubuntu 20.04 上测试的方法，显示了如何调整 javac 和 java 默认值：

$ sudo apt install openjdk-14-jdk
$ sudo apt install openjdk-8-jdk
$ java -version
openjdk version "14.0.2" 2020-07-14
OpenJDK Runtime Environment (build 14.0.2+12-Ubuntu-120.04)
OpenJDK 64-Bit Server VM (build 14.0.2+12-Ubuntu-120.04, mixed mode, sharing)
$ javac -version
javac 14.0.2
$ update-java-alternatives --list
java-1.14.0-openjdk-amd64      1411       /usr/lib/jvm/java-1.14.0-openjdk-amd64
java-1.8.0-openjdk-amd64       1081       /usr/lib/jvm/java-1.8.0-openjdk-amd64
$ 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-14-openjdk-amd64/bin/java      1411      auto mode
  1            /usr/lib/jvm/java-14-openjdk-amd64/bin/java      1411      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: 2
update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java to provide /usr/bin/java (java) in manual mode
$ sudo update-alternatives --config javac
There are 2 choices for the alternative javac (providing /usr/bin/javac).

  Selection    Path                                          Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-14-openjdk-amd64/bin/javac   1411      auto mode
  1            /usr/lib/jvm/java-14-openjdk-amd64/bin/javac   1411      manual mode
  2            /usr/lib/jvm/java-8-openjdk-amd64/bin/javac    1081      manual mode

Press <enter> to keep the current choice[*], or type selection number: 2
update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/javac to provide /usr/bin/javac (javac) in manual mode
$ java -version
openjdk version "1.8.0_275"
OpenJDK Runtime Environment (build 1.8.0_275-8u275-b01-0ubuntu1~20.04-b01)
OpenJDK 64-Bit Server VM (build 25.275-b01, mixed mode)
$ javac -version
javac 1.8.0_275

有关规范线程，请参阅 askubuntu 上的 Switch between multiple java versions。

在ubuntu中使用多个版本的java

3 个答案: