java 学习关于compare方法

public int compare(UserItem o1, UserItem o2) {
long user1Id = o1.getUserID();
long user2Id = o2.getUserID();
return user1Id > user2Id ? 1 : user1Id < user2Id ? -1 : 0;

}

排序之后为升序，

public int compare(UserItem o1, UserItem o2) {
long user1Id = o1.getUserID();
long user2Id = o2.getUserID();
return user1Id > user2Id ? -1 : user1Id < user2Id ? 1 : 0;

}

排序之后为降序