java compilation : source, target and release supported versions

Question

I may do some cross-compilations for legacy projects and I noticed with recent JDKs that we are limited to some specific versions for the source, target and release JVM arguments.
How to get the supported versions for these arguments ?

Gilges

@Robin Topper I agree that it could be better. In fact I just created this post to reduce the length of #38882580 that becomes bloat. And as this information is not present in any question of SO and that I consider it useful I would not like to just erase the information. – Gilges

If you want to make it a proper question, you should at least mention that it has something to do with Maven. Question is a bit flimsy at the moment and doesn't seem to fit the answer – Medlin

it doesn't have any relationship with Maven. The original question was broad and Maven is just a wrapper of javac. So to explain things I had to dig down in javac. – Gilges

Answer 1

Indeed the supported values depend on the major JDK version used.
You can find the information on the javac documentation of the respective major JDK versions (the links are referenced below).

Some general notes about these arguments :

• The source and the target version in the Maven configuration should not be superior to the JDK version used.
  A older version of the JDK cannot compile with a more recent version since it doesn't know its specification.

• Beware : while a recent JDK can accept as source compilation an older Java version, it doesn't mean that you can select as source any supported recent version and as target any older version that is documented as supported (see below).
  In indeed, Java versions may introduce new features that were not designed to be compatible with older Java version at compile time/run time.
  For example a JDK 11 can compile classes with 8 as source compiler version. By choosing also 8 as target compiler version, compilation will pass.
  But if you change your mind and that you want to compile with 11 as source and 8 as target, compilation will fail.
  That is not always explicitly documented in the javac documentation.

• The release argument exists from Java 9.

• As the source and the target are the same, the release argument should be favored over source and target. It is shorter to specify and it ensures a better cross compilation compatibility and whatever even if you don't do cross compilations, it will not hurt.
  For more explanations please refer to this excellent answer.

source/target/release supported versions :

For Java 7

• supported source :

1.3, 1.4, 1.5 (also 5), 1.6 (also 6), and 1.7 (also 7).

• supported target :

1.1, 1.2, 1.3, 1.4, 1.5 (also 5), 1.6 (also 6), and 1.7 (also 7).

For Java 8

• supported source :

1.3, 1.4, 1.5 (also 5), 1.6 (also 6), 1.7 (also 7), and 1.8 (also 8).

• supported target :

1.1, 1.2, 1.3, 1.4, 1.5 (also 5), 1.6 (also 6), 1.7 (also 7), and 1.8 (also 8).

For Java 9

• supported source :

1.6 (also 6), 1.7 (also 7), 1.8 (also 8), and 9.

• supported target :

1.6 (also 6), 1.7 (also 7), 1.8 (also 8) and 9.

• supported release :

6, 7, 8, and 9.

For Java 10

• supported source :

1.6 (also 6), 1.7 (also 7), 1.8 (also 8), 9, and 10.

• supported target :

1.6 (also 6), 1.7 (also 7), 1.8 (also 8), 9 and 10.

• supported release :

6, 7, 8, 9, and 10.

For Java 11

• supported source/target/release :

6, 7, 8, 9, 10, and 11.

You could have more details in the javac documentation for JDK 1.8, JDK 9, JDK 10 and JDK 11

Gilges