java string转utf-8

参考链接： java字符串之-getbytes()

.. 

/**

 * Convert input string to UTF-8, copies into buffer (at given offset).

 * Returns number of bytes in the string.

 *

 * Java's internal UTF8 conversion is very, very slow.

 * This is, rather amazingly, 8x faster than the to-string method.

 * Returns the number of bytes this translated into.

 */

public static int stringToUtf8(String s, byte[] buf, int offset) {

    if (s == null) {

        return 0;

    }

    int length = s.length();

    int startOffset = offset;

    for (int i = 0; i < length; i++) {

        int c = s.charAt(i);

        if (c < 0x80) {

            buf[offset++] = (byte) c;

        }

        else if (c < 0x800) {

            buf[offset++] = (byte)(0xc0 | ((c >> 6)));

            buf[offset++] = (byte)(0x80 | (c & 0x3f));

        }

        else {

            // Encountered a different encoding other than 2-byte UTF8. Let java handle it.

            try {

                byte[] value = s.getBytes("UTF8");

                System.arraycopy(value, 0, buf, startOffset, value.length);

                return value.length;

            }

            catch (UnsupportedEncodingException uee) {

                throw new RuntimeException("UTF8 encoding is not supported.");

            }

        }

    }

    return offset - startOffset;

}