java8集合排序

原文https://blog.csdn.net/gao1440156051/article/details/71126194  

目录

1.普通排序

2.使用增强版的Comparator接口

3.使用lamda表达式进行排序

4.多条件排序

---

1.普通排序

Collections.sort(voList);

//逆序

voList.sort(comparing(Apple::getWeight).reversed());  

2.使用增强版的Comparator接口
 

• 匿名内部类
  voList.sort(new Comparator<Apple>() {
          @Override
          public int compare(Apple o1, Apple o2) {
              return o1.getWeight() - o2.getWeight();
          }
      });
• 传递代码
  Collections.sort(voList, new PriceOrderByComparator1());
• 直接采用接口本身
  voList.sort(new PriceOrderByComparator1())
      实现Comparator带上泛型,省去类型转换的麻烦
      public class PriceOrderByComparator1 implements Comparator<SupplierUnitPriceListBySupplierIdVO> {
          @Override
          public int compare(SupplierUnitPriceListBySupplierIdVO o1, SupplierUnitPriceListBySupplierIdVO o2) {
              return cr;
          }
      }
     
  Collections.sort(humans, Comparator.comparing(Human::getName));

3.使用lamda表达式进行排序

• 普通型
  humans.sort((Human h1, Human h2) -> h1.getName().compareTo(h2.getName()));
• 简化型
  humans.sort((h1, h2) -> h1.getName().compareTo(h2.getName()));
• lamda表达式也可以使用静态方法的引用代替
  public static int compareByNameThenAge(Human lhs, Human rhs) {
      if (lhs.name.equals(rhs.name)) {
          return lhs.age - rhs.age;
      } else {
          return lhs.name.compareTo(rhs.name);
      }
  }
  humans.sort(Human::compareByNameThenAge);

4.多条件排序

• 使用lamda表达式

  List<Human> humans = new ArrayList<>();
  humans.add(new Human("Sarah", 10));
  humans.add(new Human("Jack", 12));
  humans.add(new Human("Jack", 10));

  humans.sort((lhs, rhs) -> {
              if (lhs.getName().equals(rhs.getName())) {
                  return Integer.compare(lhs.getAge(), rhs.getAge());
              } else {
                  return lhs.getName().compareTo(rhs.getName());
              }
          });

• 使用Comparator进行组合
  humans.sort(Comparator.comparing(Human::getName).thenComparing(Human::getAge));
• 自定义Comparator

  public class PriceOrderByComparator1 implements Comparator<SupplierUnitPriceListBySupplierIdVO> {
      @Override
      public int compare(SupplierUnitPriceListBySupplierIdVO o1, SupplierUnitPriceListBySupplierIdVO o2) {
          int cr = 0;
          int a =  HikPinYInUtils.getFirstSpell(o1.getTaskTypeStr()).compareTo(HikPinYInUtils.getFirstSpell(o2.getTaskTypeStr()));
          if (a != 0){
              return a;
          }else {
              int b = HikPinYInUtils.getFirstSpell(o1.getProvinceStr()).compareTo(HikPinYInUtils.getFirstSpell(o2.getProvinceStr()));
              if (b != 0){
                  return b;
              }else {
                  int c = HikPinYInUtils.getFirstSpell(o1.getCityStr()).compareTo(HikPinYInUtils.getFirstSpell(o2.getCityStr()));
                  if (c != 0){
                      return c;
                  }else {
                      int d = HikPinYInUtils.getFirstSpell(o1.getAreaStr()).compareTo(HikPinYInUtils.getFirstSpell(o2.getAreaStr()));
                      if (d != 0){
                          return d;
                      }else {
                          cr = HikPinYInUtils.getFirstSpell(o1.getBusinessName()).compareTo(HikPinYInUtils.getFirstSpell(o2.getBusinessName()));
                      }
                  }
              }
          }
          return cr;
      }
  }