public class CharPair {
    char[] c;
    
    public CharPair(char char1, char char2) {
        c = new char[2];
        c[0] = char1;
        c[1] = char2;
    }
    
    public String toString() {
        return new String(c);
    }
    
    public boolean equals(Object anObject) {
        if (anObject != null && anObject instanceof CharPair) {
            CharPair aCharPair = (CharPair)anObject;
            return c[0] == aCharPair.c[0] && c[1] == aCharPair.c[1];
        }
        else return false;
    }
    
    public int hashCode() {
        // This hash function uses the OR ("|") and LEFT SHIFT ("<<") bit operators.
        // The Java specification states that a "char" is an unsigned 16-bit value
        // that represents a Unicode character.  We can therefore take advantage of
        // all the bits available by shifting one of the chars left 16 bits (which is the
        // same as multiplying by 65536) and performing a bitwise OR on the other char
        // (which is the same as adding it).
        return Character.getNumericValue(c[0]) |
        (Character.getNumericValue(c[1]) << 16);
    }
}