Z>long a = 6l;
Z>if (new Random().nextInt() == 3) {
Z>    a = 99;
Z>    if (false)
Z>        return;
Z>    a = 10;
Z>} //Здесь else нету!
Z>a = 5;
Z>

long a = 6l;
if (new Random().nextInt() == 3) {
    a = 99;
    if (false)
        return;
    a = 10;
    a = 5;
} else
    a = 5;

long a = 6l;
if (new Random().nextInt() != 3) {
    a = 5;
} else {
    a = 99;
    if (false)
        return;
    a = 10;
    a = 5;
}