自定义一个不重复且有序的集合
public class SetList<T> extends LinkedList<T> { @Override public boolean add(T object) { if (size() == 0) { return super.add(object); } else { int count = 0; for (T t : this) { if (t.equals(object)) { count++; break; } } if (count == 0) { return super.add(object); } else { return false; } } } }