393. UTF-8 Validation 

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class Solution {
    public boolean validUtf8(int[] data) {
        int index = 0;

        while (index < data.length) {
            int num = data[index];
            if ((num >> 7 & 1) == 0) {
                // one byte
                index++;
            } else if ((num & 0b11000000) == 0b11000000 && (num >> 5 & 1) == 0 &&
                    index + 1 < data.length && (data[index + 1] >> 7 & 1) == 1 && (data[index + 1] >> 6 & 1) == 0) {
                // two bytes
                index += 2;
            } else if ((num & 0b11100000) == 0b11100000 && (num >> 4 & 1) == 0 &&
                    index + 1 < data.length && (data[index + 1] >> 7 & 1) == 1 && (data[index + 1] >> 6 & 1) == 0 &&
                    index + 2 < data.length && (data[index + 2] >> 7 & 1) == 1 && (data[index + 2] >> 6 & 1) == 0) {
                // three bytes
                index += 3;
            } else if ((num & 0b11110000) == 0b11110000 && (num >> 3 & 1) == 0 &&
                    index + 1 < data.length && (data[index + 1] >> 7 & 1) == 1 && (data[index + 1] >> 6 & 1) == 0 &&
                    index + 2 < data.length && (data[index + 2] >> 7 & 1) == 1 && (data[index + 2] >> 6 & 1) == 0 &&
                    index + 3 < data.length && (data[index + 3] >> 7 & 1) == 1 && (data[index + 3] >> 6 & 1) == 0) {
                // four bytes
                index += 4;
            } else {
                break;
            }
        }

        return index == data.length;
    }
}

References

393. UTF-8 Validation