Class Single

src/jvm/clojure/lang/TransformerIterator.java:137–169

}

private static class Single implements Buffer {
    private volatile Object val;

    public Single(Object o) {
        this.val = o;
    }

    public Buffer add(Object o) {
        if (val == NONE) {
            val = o;
            return this;
        } else {
            return new Many(val, o);
        }
    }

    public Object remove() {
        if(val == NONE) {
            throw new IllegalStateException("Removing object from empty buffer");
        }
        Object ret = val;
        val = NONE;
        return ret;
    }

    public boolean isEmpty() {
        return val == NONE;
    }

    public String toString() {
        return "Single: " + val;
    }
}

private static class Many implements Buffer {
    private final Queue vals = new LinkedList();