更改java编译器版本

Question

I get this error when running my Java application

Global : Unsupported major.minor version 52.0

When I checked my Java version, I found that it was different from the compiler version

java -version
# java version "1.7.0_65"
# OpenJDK Runtime Environment (IcedTea 2.5.1) (7u65-2.5.1-4ubuntu1~0.12.04.2)
# OpenJDK Server VM (build 24.65-b04, mixed mode)
javac -version
# javac 1.8.0_20

How do I downgrade the Java compiler?

Answer 1

Open a console. Type

sudo update-alternatives --config javac

After entering your root password you can enter the number of a javac with "java-7" in its name.

Edit: You could also update-alternatives --config java to choose a newer JVM that is compatible to Java 8 bytecode.

Answer 2

You don't need to downgrade the compiler; you just need to tell the compiler to produce classes that a Java 7 JVM will understand. Use the options -source 7 -target 7 when running javac .

Answer 3

I'm assuming you are using linux,

sudo update-alternatives --config javac

Then you can type your choice. If you get message like 'There is only one alternative...' then you should type to the terminal

sudo update-alternatives --install "/usr/bin/javac" "javac" "/(your java home)/bin/javac" 1