1.根据集合的某个属性值，给集合做排序.
1.实体类要实现Comparable接口
代码语言：javascript复制public class IndustryInfo implements Comparable<IndustryInfo>{
private String code;
private String name;
private Integer num;
private String str;
@Override
public int compareTo(IndustryInfo o) {
return 0;
}
//get set 省略
}2.按照num逆序排列
代码语言：javascript复制 List<IndustryInfo> listRe = list.stream().sorted(Comparator.comparing(IndustryInfo::getNum).reversed()).collect(Collectors.toList());2.排除某个特定元素
代码语言：javascript复制List<Map<String, Object>> list8 = list7.stream().filter(map -> !map.get("name").toString().equals("高新技术企业")).collect(Collectors.toList());3.获取某个特定元素
代码语言：javascript复制 Map<String, Object> map1 = list2.stream().filter(map -> map.get("name").toString().equals("黑榜企业")).collect(Collectors.toList()).get(0);4.根据list中map的某个属性值排序list
代码语言：javascript复制 List<Map> list44= list4.stream()
.sorted((map1, map2) -> map1.get("cnt").toString().compareTo(map2.get("cnt").toString())).collect(Collectors.toList());5.根据list中map的某个属性值进行过滤
代码语言：javascript复制 List<Map> collect1 = list6.stream().filter(map -> map.get("entStatus").toString().indexOf("在营") != -1).collect(Collectors.toList());6.根据list中map的某个属性值进行求和
代码语言：javascript复制 int sumZaiYing = collect1.stream().mapToInt(map -> Integer.valueOf(map.get("cnt").toString())).sum();7.根据map的某个value来分类List<Map<String,Object>>
代码语言：javascript复制Map<Object, List<Map<String, Object>>> age = list.stream().collect(Collectors.groupingBy(map -> map.get("age")));8.根据对象的某个属性值来分类List
代码语言：javascript复制Map<String, List<User>> collect1 = list2.stream().collect(Collectors.groupingBy(User::getProvince));9.根据对象属性筛选最大值
代码语言：javascript复制ApprovalLogVo approvalLogVo = onlyPass.stream().max(Comparator.comparing(ApprovalLogVo::getApprovalTime)).get();
ApprovalLogVo maxVo=
onlyPass.stream().collect(Collectors.maxBy(Comparator.comparing(ApprovalLogVo::getApprovalTime))).get();10.汇总集合中的某个对象属性
代码语言：javascript复制public static void main(String[] args) {
List<DistributedLockDO> list = new ArrayList<>();
list.add(new DistributedLockDO("key1","ip11:80911",11L));
list.add(new DistributedLockDO("key2","ip22:80922",11L));
list.add(new DistributedLockDO("key3","ip33:80933",11L));
List<Object> collect = list.stream().flatMap(lockDO -> Arrays.stream(lockDO.getLockValue().split(":"))).collect(Collectors.toList());
System.out.println(collect.toString());
}或者下面这种拆开写，可以过滤什么的，起手flatmap不好处理其他的逻辑
代码语言：javascript复制 List<String> collect = list.stream().map(DistributedLockDO::getLockValue).filter(v -> StringUtils.isNotBlank(v))
.flatMap(v -> Arrays.stream(v.split(":"))).collect(Collectors.toList());输出为：[ip11, 80911, ip22, 80922, ip33, 80933]
11. Predicate
代码语言：javascript复制 public static void main(String[] args) {
List<Integer> list = Arrays.asList(1, 2, 3, 4, 5, 5, 7, 12);
List<Integer> integers = biggerThan5(list, integer -> integer > 5);
System.out.println(integers);
}
public static List<Integer> biggerThan5(List<Integer> list, Predicate<Integer> predicate) {
return list.stream().filter(predicate).collect(Collectors.toList());
}
