Java 6 support?

[eis]

Can this be made to work with Java 6? That is the oldest major java release that would have Azul openjdk distribution available (https://www.azul.com/downloads/?package=jdk#download-openjdk)

[eis]

Notes:

1. Maven version last to support java 6 is 3.2.5

Sources:

• https://stackoverflow.com/questions/36141186/what-version-of-maven-is-compatible-with-java-6
• https://maven.apache.org/docs/history.html

2. Maven 3.2.5 will default to http link to central which is not longer supported - this can be worked around with explicit https configuration

3. Java 6 will error on connecting to central since it will require tls 1.2, and Java 6 only supports up to 1.1 (Java 7 supports tls 1.2 but it is disabled by default)

Sources:

• https://stackoverflow.com/questions/50824789/why-am-i-getting-received-fatal-alert-protocol-version-or-peer-not-authentic/52614215
• https://central.sonatype.org/faq/tls-info/

To work around this, we can use insecure endpoint as explained in http://insecure.repo1.maven.org.

4. On compiling we get errors since "Diamond types" and multi-catches are not supported in Java 6. Thus, this code will not build on java 6. However, we can downgrade these features.
5. Compiler-plugin, surefire-plugin and hamcrest-library versions need to be downgraded if they are to be run on Java 6.

[eis]

f677da3 shows that this could be done. However, too many sacrifices for it to be in master.

[eis]

Another alternative which could enable using latest java + plugins but build the code with older jdk would be to use toolchains: https://blog.bmarwell.de/en/testing-maven-with-toolchain-and-github-actions/