how to get timestamp from firebase code example

Example: timestamp firebase

// Example 4: Compute Timestamp from Java `System.currentTimeMillis()`.

long millis = System.currentTimeMillis();

Timestamp timestamp = 
  Timestamp.newBuilder()
           .setSeconds(millis / 1000)
           .setNanos((int)(millis % 1000 * 1_000_000))
           .build();