Lazy field initialization with lambdas

Question

I would like to implement lazy field initialization (or deferred initialization) without an if statement and taking advantage of lambdas. So, I would like to have the same b

Answer 1

Well, I don't really suggest having no "if", but here's my take on the matter:

One simple method is to use an AtomicReference (the ternary operator is still like an "if"):

private final AtomicReference lazyVal = new AtomicReference<>();

void foo(){
    final Something value = lazyVal.updateAndGet(x -> x != null ? x : expensiveCreate());
    //...
}

But then there is the whole thread safety magic that one might not need. So I'd do it like Miguel with a little twist:

Since I like simple one-liners, I simply use a ternary operator (again, reads like an "if") but I'd let Java's evaluation order do its magic to set the field:

public static  Supplier lazily(final Supplier supplier) {
    return new Supplier() {
        private T value;

        @Override
        public T get() {
            return value != null ? value : (value = supplier.get());
        }
    };
}

gerardw's field-modification example above, that works without an "if", can be further simplified too. We don't need the interface. We just need to exploit above "trick" again: An assignment operator's result is the assigned value, we can use brackets to force evaluation order. So with the method above it's just:

static  Supplier value(final T value) {
   return () -> value;
}


Supplier p2 = () -> (p2 = value(new Point())).get();

Note that you cannot inline the "value(...)" method without losing the laziness.