public boolean pop() {
    if (isEmpty()) {
      throw new IllegalArgumentException("Error: Queue is Empty!");
    }
    final boolean ret = data[head];
    head = (head + 1) % data.length;
    size--;
    if (size < data.length / 4 && data.length / 2 >= minLen) {
      resize(data.length / 2);
    }
    return ret;
  }
pop value from the front of queue.

@return value in the front
library-udf/src/main/java/org/apache/iotdb/library/util/BooleanCircularQueue.java