stream流如何对集合排序(多字段排序(升序和降序)---(空值放最后))的效果呢?

stream对集合排序的实现思路

借助Comparator.comparing方法即可对集合排序

 
//1.实体类
public class student{
	private String id;
	private String name;
}

//2.集合数据
student student4 = new student();
//student4.setId("8");
student4.setName("maomao");
student student5 = new student();
student5.setId("9");
student5.setName("狗狗");
student student6 = new student();
student6.setId("10");
student6.setName("你最牛");
list<student> list2 = new ArrayList<>();
list2.add(student4);
list2.add(student5);
list2.add(student6);
System.out.println(list2);
 
//3.集合排序,空值最后

list2 = list2.stream()
        .sorted(Comparator.comparing(student::getId,
		          Comparator.nullsFirst(String::compareTo)).reversed())
        .collect(Collectors.toList());//倒序
                    
 list2 = list2.stream()
         .sorted(Comparator.comparing(student::getId,Comparator.nullsLast(String::compareTo)))
         .collect(Collectors.toList());//升序   
                    
list2 = list2.stream()
         .sorted(Comparator.comparing(student::getId,Comparator.nullsLast(String::compareTo))
		                   .reversed().thenComparing(student::getName))
         .collect(Collectors.toList());//id降序，名字升序