java框架选型 Guava vs Lambdaj

需求

查询用户最近的中奖信息并返回中奖名单列表

纯Java7实现

// 返回用户最近4条的中奖纪录

List<UserWinning> uwList = Lists.newArrayList(new UserWinning(userId, 1), new UserWinning(userId, 2), new UserWinning(userId, 3), new UserWinning(userId, 1));

//提取奖品ID

List<Integer> awardIdLsit = new ArrayList<>(uwList.size());

for(UserWinning uw : uwList){

awardIdLsit.add(uw.getAwardId());

}

//根据奖品ID查询奖品

List<Award> awardList = Lists.newArrayList(new Award(1, "奖品一"), new Award(2, "奖品二"), new Award(3, "奖品三"));

//List --> Map 得到奖品ID和奖品名称Map

Map<Integer, String> awardIdNameMap = new HashMap<>(awardList.size());

for(Award a : awardList){

awardIdNameMap.put(a.getId(), a.getName());

}

评价

感觉非常繁琐特别是当你习惯了Java8的函数式编程后

Guava实现

List<UserWinning> uwList = Lists.newArrayList(new UserWinning(userId, 1), new UserWinning(userId, 2), new UserWinning(userId, 3), new UserWinning(userId, 1));

//提取奖品ID

评价

代码不够简洁，看的时候还是容易被这些匿名内部类干扰，虽然写的时候也很流畅。优点是返回的集合都是不可变的。

Lambdaj实现

List<UserWinning> uwList = Lists.newArrayList(new UserWinning(userId, 1), new UserWinning(userId, 2), new UserWinning(userId, 3), new UserWinning(userId, 1));

//提取awardIdList

List<Integer> awardIdList = extract(uwList, on(UserWinning.class).getAwardId());

System.out.println(awardIdList);

List<Award> awardList = Lists.newArrayList(new Award(1, "奖品一"), new Award(2, "奖品二"), new Award(3, "奖品三"));

//List -> Map

Map<Integer, Award> idAwardMap = index(awardList, on(Award.class).getId());

//得到奖品名称列表

List<String> nameList = convert(awardIdList, new Converter<Integer, String>() {

@Override

public String convert(Integer from) {

return idAwardMap.get(from).getName();

}