后端集合操作汇总

   1、获得集合中某一列数据形成一个新的集合

List<String> setCode =resultList.stream().map(e -> e.getSetCode()).collect(Collectors.toList());
2、集合中对象类型转换

List<RealityTaskEx> exList = ModelConverterUtils.convert(taskList, RealityTaskEx.class);

public static <T> List<T> convert(Collection<?> sources, Class<T> targetClass) {
    if (sources == null) {
        return null;
    }
    List<T> targets = Lists.newArrayList();
    if (!CollectionUtils.isEmpty(sources)) {
        targets = sources.stream().map(x -> convert(x, targetClass)).collect(Collectors.toList());
    }
    return targets;
}
3、数组转成集合

List<String> list = Arrays.asList(person);//String[] person

// List<String> 转成List<Long>
List<Long> amList = list.stream().map(s -> Long.parseLong(s.trim())).collect(Collectors.toList());
4、集合根据某个字段去重

personList.stream().distinct().collect(Collectors.toList());
5、筛选符合条件的数据集合

List<RealitySchedule> schedule =sheduleList.stream().filter(e -> e.getSetId() == Long.parseLong(realitySet[0])).collect(Collectors.toList());
//将集合转换成String类型

nameSet +=String.join(",",pmNameList.stream().distinct().filter(Objects::nonNull).collect(Collectors.toList()));
6、集合中是否包含某个对象值

Boolean exist= taskTypeList.stream().filter(t->t.equals(ConstantEnum.TASK_TYPE_MORING.getCode())).findAny().isPresent();

7、获取yml文件中的值

import org.springframework.beans.factory.annotation.Value;

@Value("${spring.application.name}")
private String applicationName;
8、得到集合中的多个值

List<String> outBoxList = boxes.stream().map(s ->s.getId()+","+s.getBranchId()).collect(Collectors.toList())

outBoxList.stream().forEach(u ->{
    // 根据逗号分开多个参数
    String[] boxBranch = u.split(",");
    // 查询集合中是否存在某个对象
    OutWarehouseDetail detail =outList.stream().filter(o ->o.getBoxId().equals(boxBranch[0])).findFirst().orElse(null);
 }）
9、集合切片

<!--list 切片-->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-collections4</artifactId>
    <version>4.4</version>
</dependency>

import org.apache.commons.collections4.ListUtils;

   // 根据需求，将款箱三列展示
                        List<List<BaseCashBoxInfoEx>> partition = ListUtils.partition(returnList,3);
                        if(CollectionUtils.isNotEmpty(partition)){
                                List<BaseCashBoxInfoEx> first =new ArrayList<>();
                                List<BaseCashBoxInfoEx> second = new ArrayList<>();
                                List<BaseCashBoxInfoEx> third =new ArrayList<>();
                                partition.stream().forEach( p ->{
                                    int count =p.size();
                                    if(count == 1){
                                        first.add(p.get(0));
                                    }else if(count == 2){
                                        first.add(p.get(0));
                                        second.add(p.get(1));
                                    }else{
                                        first.add(p.get(0));
                                        second.add(p.get(1));
                                        third.add(p.get(2));
                                    }
                                });
                                ex.setFirstBox(first);
                                ex.setSecondBox(second);
                                ex.setThirdBox(third);
                         }