@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Bigram other = (Bigram) obj;
		if (word1 == null) {
			if (other.word1 != null)
				return false;
		} else if (!word1.equals(other.word1))
			return false;
		if (word2 == null) {
			if (other.word2 != null)
				return false;
		} else if (!word2.equals(other.word2))
			return false;
		return true;
	}