Jdk8 Code片段

相关系列文章参考：

http://www.importnew.com/tag/java8

1.时间戳转时间字符：

DateTimeFormatter df = DateTimeFormatter.ofPattern(Constants.DATE_YMD_HMS);
String k = df.format(LocalDateTime.ofInstant(Instant.ofEpochSecond(1535355250L), ZoneId.of("Asia/Shanghai")));

2.Optional的写法：（参考：Java8 如何正确使用 Optional）

以前：

public static String getChampionName(Competition comp) throws IllegalArgumentException {
    if (comp != null) {
        CompResult result = comp.getResult();
        if (result != null) {
            User champion = result.getChampion();
            if (champion != null) {
                return champion.getName();
            }
        }
    }
    throw new IllegalArgumentException("The value of param comp isn't available.");
}

现在：

public static String getChampionName(Competition comp) throws IllegalArgumentException {
    return Optional.ofNullable(comp)
            .map(c->c.getResult())
            .map(r->r.getChampion())
            .map(u->u.getName())
            .orElseThrow(()->new IllegalArgumentException("The value of param comp isn't available."));
}



 TestService service = testServiceList.stream().filter(x -> x.isSupport(supportBean))
                .sorted(Comparator.comparing(TestService::getPriority))
                .map(Optional::ofNullable)
                .findFirst()
                .flatMap(Function.identity())
                .orElse(null);

3.forEach轮询Map对象：

        Map one = Maps.newHashMap();
        for(int k=0;k<10;k++) {
            one.put("key" + k, "value" + k);
        }
        one.forEach((key,value)->{
            System.err.println(key + "    :   " + value);
        });