Preconditions

Utility methods for precondition checks.

Methods in this class return Result values when a condition is violated. Use these checks for programmer errors (invalid arguments or illegal state), and propagate the failure contract to callers.

Example:

    var argOk = Preconditions.checkArgument (port > 0, "port must be positive");
    if (argOk.isError ()) {
        return;
    }
    var stateOk = Preconditions.checkState (is_initialized, "not initialized");
    if (stateOk.isError ()) {
        return;
    }