public class SupplementaryCharTest3 {
    public static void main(String[] args) {
        char[] ch = new char[]{(char)0xD801, (char)0xDC00};
        
        int codePoint = Character.toCodePoint(ch[0], ch[1]);
        System.out.format("UTF-16 %X %X -> %X\n", (int)ch[0], (int)ch[1], codePoint);

        String str1 = new String(new int[]{codePoint}, 0, 1);
        String str2 = new String(ch);
        System.out.format("U+0010400 == UTF-16 D801 DC00 : %b%n", str1.equals(str2));
    }
}