FieldCanBeStatic

final fields initialized with a literal can elide a per-instance reference by adding the static keyword. Since the field is final it is unmodifiable and since its initializer is a literal the value is immutable and thus sharing a per-class field is safe. This also allows a simpler constant load bytecode instead of a field lookup.

That is, prefer this:

static final String string = "string";
static final int number = 42;

Not this:

final String string = "string";
final int number = 42;