如何降级 Java 版本，在其他操作系统应该也适用
题图用于怀旧
我也是因为在运行 neo4j 的时候遇到了 Java 版本的问题：
> ./neo4j console...WARNING! You are using an unsupported Java runtime.* Please use Oracle(R) Java(TM) 11, OpenJDK(TM) 11 to run Neo4j....
复制代码
查看本地版本：
> java -versionjava version "15.0.2" 2021-01-19Java(TM) SE Runtime Environment (build 15.0.2+7-27)Java HotSpot(TM) 64-Bit Server VM (build 15.0.2+7-27, mixed mode, sharing)
复制代码
一开始的想法是卸载掉当前的版本，重新安装。后来在 stackoverflow 上找到了
How to downgrade JDK on MacOShttps://stackoverflow.com/questions/46513639/how-to-downgrade-java-from-9-to-8-on-a-macos-eclipse-is-not-running-with-java-9
You don't need to down grade. You can run more than one version of Java on MacOS. You can set the version of your terminal with this command in MacOS.
# List Java versions installed/usr/libexec/java_home -V
Matching Java Virtual Machines (4): 15.0.2 (x86_64) "Oracle Corporation" - "Java SE 15.0.2" /Library/Java/JavaVirtualMachines/jdk-15.0.2.jdk/Contents/Home 14.0.1 (x86_64) "Oracle Corporation" - "Java SE 14.0.1" /Library/Java/JavaVirtualMachines/jdk-14.0.1.jdk/Contents/Home 11.0.7 (x86_64) "Oracle Corporation" - "Java SE 11.0.7" /Library/Java/JavaVirtualMachines/jdk-11.0.7.jdk/Contents/Home 1.8.0_51 (x86_64) "Oracle Corporation" - "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_51.jdk/Contents/Home/Library/Java/JavaVirtualMachines/jdk-15.0.2.jdk/Contents/Home
复制代码
发现自己的笔记本上有多个 JDK 的版本，然后在 .zshrc 里面添加
# Java 11export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk-11.0.7.jdk/Contents/Home
复制代码
再运行
就可以把 Java 的版本“downgrade” 到 Java 11
后来又遇到了
> ./neo4j console...... was successfully initialized, but failed to start. Please see the attached cause exception "Address already in use"
复制代码
使用 ps 命令查看进程，然后 kill 掉残余的 neo4j
> ps aux | grep neo4j...> bin kill -9 54839
复制代码
再次启动，终于看到了
> ./neo4j console --verbose...... INFO Started.
复制代码
我后来把 Java 的版本改回 15.0.2，启动 neo4j，虽然有警告，但是没有其他的影响。
评论