There are at least two ways you can verify that.
One is to put a print statement at the start of your static initialiser. Since the default value of fields is null, however, that is not really that informative.
The second way is to view the bytecode with javap -c Foo The third is to find the section of the Java Language Specification (JLS) about initialisers. That’s 3 out of 2. Beware: the JLS is not easy to read.