If this happens so often, then it
 should be easy to post an example.

    The only scenario I can think of where a `semifinal' might
help is when there are multiple constructors, and one of them
chains to another before setting the variable:

    private Something instanceVariable;

    public SomeClass() {
       doLotsOfStuff();
       instanceVariable = new Something(42);
    }

    public SomeClass(int value) {
       this();
       instanceVariable = new Something(value);
    }

The obvious answer in this case is to rearrange responsibilities:

    private Something instanceVariable;

    public SomeClass() {
       this(42);
    }

    public SomeClass(int value) {
       doLotsOfStuff();
       instanceVariable = new Something(value);
    }

    Or perhaps you're worried about running a loop that might
set the variable several times, as in:

    private Something instanceVariable();

    public SomeClass(Collection<Something> things) {
       for (Something thing : things)
           if (thing.somePredicate())
               instanceVariable = thing;
    }

This is easily fixed by introducing a local variable:

    private Something instanceVariable;

    public SomeClass(Collection<Something> things) {
       Something chosen = null;
       for (Something thing : things)
           if (thing.somePredicate())
               chosen = thing;
       instanceVariable = chosen;
    }

    If you have some other situation that seems to cry out for
a `semifinal' variable, please post it.

    Simplicity: If the rules are easy to state ("one and only
one assignment") things are easier for both the compiler and
for the human reader.  Error detection: Did the programmer truly
intend to make multiple assignments, or did some execution path
escape his notice?  Maybe other reasons, too.

    Let's turn the question around: What benefit would accrue
from *allowing* `semifinal' variables?

because final means FINAL, not to be changed again. If you need to do
some temporary calculation before coming up with the value, put the
temps is a local variables, then mark the result final.