过滤3个字节以上的utf-8字符

/**
* 过滤掉超过3个字节的UTF8字符
* @param text
* @return
* @throws UnsupportedEncodingException
*/
public static String filterOffUtf8Mb4(String text) throws UnsupportedEncodingException {
byte[] bytes = text.getBytes("utf-8");
ByteBuffer buffer = ByteBuffer.allocate(bytes.length);
int i = 0;
while (i < bytes.length) {
short b = bytes[i];
if (b > 0) {
buffer.put(bytes[i++]);
continue;
}

b += 256; // 去掉符号位

if (((b >> 5) ^ 0x6) == 0) {
buffer.put(bytes, i, 2);
i += 2;
} else if (((b >> 4) ^ 0xE) == 0) {
buffer.put(bytes, i, 3);
i += 3;
} else if (((b >> 3) ^ 0x1E) == 0) {
i += 4;
} else if (((b >> 2) ^ 0x3E) == 0) {
i += 5;
} else if (((b >> 1) ^ 0x7E) == 0) {
i += 6;
} else {
buffer.put(bytes[i++]);
}
}
buffer.flip();
return new String(buffer.array(), "utf-8");
}