Java List 排序sort 和sorted方法说明

Java List 排序Sort 和Sorted

1、sort: list.sort 方法是list方法对原有list 元素顺序位置进行更改排序

　　如：

    listP.sort((x1,x2)->x1.getName().compareTo(x2.name));

2、sorted: sorted 方法是对list转换成stream流的方法，不对有有list元素排序，而是返回一个排序后的新list：

如：

List<Fruit> listP2 = listP.stream().sorted(Comparator.comparing(Fruit::getName).reversed().thenComparing(Fruit::getWeight)).collect(Collectors.toList());

如果想第二个排序字段倒序排可以如下写法
List<Fruit> listP2 = listP.stream().sorted(Comparator.comparing(Fruit::getName).reversed()
　　　　　　　　　　　　　　　　　　　　　　　　.thenComparing(Comparator.comparing(Fruit::getWeight).reversed())).collect(Collectors.toList());




下面用多种方式实例进行说明

try {
         Fruit p1 = new Fruit();
         p1.setName("apple");
         p1.setWeight(8);
 
         Fruit p2 = new Fruit();
         p2.setName("apple");
         p2.setWeight(13);
         Fruit p3 = new Fruit();
         p3.setName("pear");
         p3.setWeight(10);
 
         Fruit p4 = new Fruit();
         p4.setName("pear");
         p4.setWeight(16);
         Fruit p5 = new Fruit();
         p5.setName("wang");
         p5.setWeight(10);
 
         Fruit p6 = new Fruit();
         p6.setName("banana");
         p6.setWeight(2);
 
         List<Fruit> listP = Arrays.asList(p1, p2, p3, p4, p5, p6);
        // list.sort 对原有list 元素顺序位置进行更改排序
         // lamda表达式实现 Comparator  简要主法
         listP.sort((x1,x2)->x1.getName().compareTo(x2.name));
         // lamda 表达式实现自定义方法
         listP.sort((x1,x2)-> {
           if(x1.getWeight()>x2.getWeight()){
               return 1;
           } else if(x1.getWeight()<x2.getWeight()){
               return -1;
           }else{
               return 0;
           }
         });
 
         //lamda 表达式 显示实现 comparator方法
         listP.sort(new Comparator<Fruit>() {
             @Override
             public int compare(Fruit o1, Fruit o2) {
                 return o1.getName().compareTo(o2.getName());
             }
         });
 
         // list sort 实现多字段排序
         Comparator<Fruit> nameComparator=Comparator.comparing(x-> x.getName());
         Comparator<Fruit> weightComparator=Comparator.comparing(x-> x.getWeight());
         listP.sort(nameComparator.thenComparing(weightComparator));
 
 
         // list-stream()->sorted 进行排序反回排序后新list，原list元素顺序不变
         List<Fruit> listP2 = listP.stream().sorted(Comparator.comparing(Fruit::getName).reversed().thenComparing(Fruit::getWeight)).collect(Collectors.toList());
 
     } catch (Exception e) {
         e.printStackTrace();
     }
 
 
 }

　　3、List<String> list 排序下面代码实例

  String[] strC = new String[]{"账单优惠", "现金", "账单减免", "扫码支付", "团购", "会员卡", "银行卡"};
        List<String> listCategory = new ArrayList<>();
        listCategory = Arrays.asList(strC);
        List<String> list2 = listCategory.stream().sorted(String::compareTo).collect(Collectors.toList());
        List<String> list3 = listCategory.stream().sorted((x1, x2) ->
        {
            return x1.compareTo(x2);
        }).collect(Collectors.toList());

        Collections.sort(listCategory);
        Collections.reverse(listCategory);