public int popFirst() {
        if (mHead == mTail) throw new ArrayIndexOutOfBoundsException();
        int result = mElements[mHead];
        mHead = (mHead + 1) & mCapacityBitmask;
        return result;
    }
Remove first integer from front of the CircularIntArray and return it.

@return The integer removed.
@throws ArrayIndexOutOfBoundsException if CircularIntArray is empty.
android/android_framework/base/src/main/java/github/tornaco/android/thanos/core/util/collection/CircularIntArray.java