Design a multi-timer using single underlying timer

You are given a `Timer` class that has access to a *single* underlying system timer API that can only keep **one active timer at a time**. ### Underlying single-timer primitives (already available) ```java class Timer { // Schedule ONE timer to fire at `timestamp` (absolute time). // If called again, it overrides/cancels the previously scheduled system timer. private void setTimer(long timestamp); // Called automatically when the currently scheduled system timer expires. private void handleTimer(); // Returns current time as an absolute timestamp (same unit as setTimer). private long getCurrentTime(); // Public API: users can call this to schedule MANY timers. public void setNewTimer(long timestamp); } ``` ### Requirements - Users can only call `setNewTimer(timestamp)`. - `setNewTimer` must support **multiple** outstanding timers. - When any user timer expires, `handleTimer()` should be invoked (once per expired user timer). - You must implement the logic of the four methods so that multiple user timers are correctly managed on top of the single underlying `setTimer`. ### Clarifications you may assume - `timestamp` is an **absolute** time value (e.g., epoch milliseconds) comparable to `getCurrentTime()`. - Multiple user timers may share the same timestamp. - If a timer is set for a time ≤ `getCurrentTime()`, it should fire “immediately” (as soon as the system can schedule it). Discuss data structures, time/space complexity, and important edge cases (e.g., overrides, duplicate timestamps, and concurrency if relevant).