How to resolve: [javac] This version of java does not support the classic compiler; upgrading to modern

Question

Our company recently moved our build environment from our local machine to a docker shell. It caused an old tool that used ant and java to compile to fail. I'm not familiar with compiling java so please bear with me.

We've installed:

• ant version 1.7.1
• java and javac version 1.7.0_141

Now the tool compiles but has following error/warning:

[javac] This version of java does not support the classic compiler; upgrading to modern

Would you know what is the cause of this? Is it a mismatch between ant 1.7.1 vs. the java version?

I added fork="true" in the ant build .xml file, and the error/warning went away. I don't understand why?

<javac destdir="classes"
       debug="on"
       includeantruntime="false"
       fork="true" >                 // <-- Somehow fork="true" got rid of warning/error.

Answer 1

通过在build .xml中添加以下内容来解决：

<property name="build.compiler" value="modern" />