public class Pair<T> //这句挺困惑,Pair不就是一个类型吗?它怎么还能有个可变类型T呢!
{
public Pair() { first = null; second = null; }
public Pair(T first, T second) { this.first = first; this.second = second; }

public T getFirst() { return first; }
public T getSecond() { return second; }

public void setFirst(T newValue) { first = newValue; }
public void setSecond(T newValue) { second = newValue; }

private T first;
private T second;
}