Java處理List的雙層循環(huán)程序員經(jīng)常遇到，一般都是當(dāng)兩個(gè)List某個(gè)值滿足某條件時(shí)候，進(jìn)行相應(yīng)的處理；
1.list和map之間的相互轉(zhuǎn)換
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/** * 兩個(gè)List對(duì)象當(dāng)id相同的時(shí)候(注意是兩個(gè)對(duì)象,而非兩個(gè)集合) * @param husbands * @param wives */private static void test8(List<Husband> husbands, List<Wife> wives) { List<Family> families = Lists.newArrayList(); //將wives轉(zhuǎn)換為map,這里的key一定要唯一,即為familyId Map<Integer, Wife> wifeMap = wives.stream().collect(toMap(w -> w.getFamilyId(), w -> w)); families = husbands.stream().map(husband -> { Family family = new Family(); Wife wife = wifeMap.get(husband.getFamilyId()); family.setFamilyId(wife.getFamilyId()); family.setHusbandName(husband.getHusbandName()); family.setWifeName(husband.getWifename()); return family; }).collect(Collectors.toList());} |
2.java8中的
groupingBy
counting
mapToDouble
filter
sum等函數(shù)方法的使用
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//蘋果顏色對(duì)應(yīng)的數(shù)量Map<String, Long> collect = appleVos.stream().collect(groupingBy(AppleVo::getColor, counting()));// 過濾掉顏色為黑色的蘋果，并匯總好蘋果的總金額Double sum = appleVos.stream().filter(i -> "black".equals(i.getColor())).mapToDouble(AppleVo::getPrice).sum(); |
補(bǔ)充知識(shí)：java8新技術(shù)：數(shù)據(jù)流式處理之兩個(gè)list集合多對(duì)多遍歷關(guān)聯(lián)
自用測(cè)試方法
說明一下：list1和list2兩個(gè)集合進(jìn)行匹配，將list2中的對(duì)應(yīng)的值取出，使list1中的每條數(shù)據(jù)都有對(duì)應(yīng)的list2中的name值，list1為主集合，數(shù)據(jù)需全部展示；
注意：若list1的數(shù)量多于list2,并且數(shù)據(jù)匹配不上，則多出來的會(huì)在list3中為null;
以上這篇Java8處理List的雙層循環(huán)問題就是小編分享給大家的全部?jī)?nèi)容了，希望能給大家一個(gè)參考，也希望大家多多支持服務(wù)器之家。
原文鏈接：https://blog.csdn.net/wb_zjp283121/article/details/87938662
