list快速轉map
Map<String, GddResult> gddMap = gddList.stream().collect(Collectors.toMap(g -> g.getGoodsCode(), g -> g, (k1, k2) -> k1));
字典排序
List<String> list = new ArrayList<String>();
list.add("a2Y12345");
list.add("3X12345");
list.add("1Z12345");
List<String> disProductList = list.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(o -> o))), ArrayList::new));
list 先分組然後轉map
Test t1= new Test("001","1","Y1","1");
Test t2= new Test("001","2","Y1","2");
Test t3= new Test("002","1","Y1","3");
Test t4= new Test("002","2","Y1","4");
Test t5= new Test("001","1","Y2","5");
Test t6= new Test("002","1","Y2","6");
List<Test> list = new ArrayList<>();
list.add(t1);
list.add(t2);
list.add(t3);
list.add(t4);
list.add(t5);
list.add(t6);
Map<String, Map<String, Map<String, String>>> collect = list.stream().collect(Collectors.groupingBy(Test::getOrgCode, Collectors.groupingBy(Test::getChannelId, Collectors.toMap(Test::getProductCode, Test::getD))));
System.out.println(JSON.toJSON(collect));
輸出
{"001":{"1":{"Y1":"1","Y2":"5"},"2":{"Y1":"2"}},"002":{"1":{"Y1":"3","Y2":"6"},"2":{"Y1":"4"}}}
日期類型排序
List<Date> datas = new ArrayList<>();
String s1 = "2019-08-10 22:18:22";
String s2 = "2018-08-10 22:18:22";
String s3 = "2017-08-10 22:19:22";
DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
datas.add(df.parse(s1));
datas.add(df.parse(s2));
datas.add(df.parse(s3));
datas.sort((a,b)-> b.compareTo(a));
datas.forEach(d->{
System.out.println(d);
});
對象類型排序
ss.sort((a, b) -> b.getAge() - a.getAge());
inventory.sort(comparing(Apple::getWeight).reversed());
//返回 對象集合以類屬性一降序排序 注意兩種寫法
list.stream().sorted(Comparator.comparing(類::屬性一).reversed());//先以屬性一升序,結果進行屬性一降序
list.stream().sorted(Comparator.comparing(類::屬性一,Comparator.reverseOrder()));//以屬性一降序
按照兩個屬性排序
//返回 對象集合以類屬性一升序 屬性二升序
list.stream().sorted(Comparator.comparing(類::屬性一).thenComparing(類::屬性二));
//返回 對象集合以類屬性一降序 屬性二升序 注意兩種寫法
list.stream().sorted(Comparator.comparing(類::屬性一).reversed().thenComparing(類::屬性二));//先以屬性一升序,升序結果進行屬性一降序,再進行屬性二升序
list.stream().sorted(Comparator.comparing(類::屬性一,Comparator.reverseOrder()).thenComparing(類::屬性二));//先以屬性一降序,再進行屬性二升序
//根據機構,渠道,商品分組分組,最後的list中正常情況有且只有一個對象
Map<String, Map<String, Map<String, List<StockProductBuisnessDto>>>> lastPriceMap = lastPriceList.stream().collect(Collectors.groupingBy(StockProductBuisnessDto::getOrgCode, Collectors.groupingBy(StockProductBuisnessDto::getChannelId, Collectors.groupingBy(StockProductBuisnessDto::getProductCode))));