The same elements of the list set are summed by other fields

Question: There are fields with the same value in a certain list collection, how to find the sum of the values ​​of other fields of the same field?

List:

**实体**
public class A{
    
    
	private Long total;
	private List<Way> ways;
}

**部分代码**
List<A> a = new ArrayList<>();
/**
{"total":"10",
 "ways":[{"id":"1"}]
},
{"total":"5",
 "ways":[{"id":"1"}]
},
{"total":"3",
 "ways":[{"id":"2"}]
}
**/
//现在想把ways相同的合并成一个新的way，并且total相加即前两个10+5
List<a> afterA = a.stream.collect(Collectors.toMap(A::getWay,e->e,(o1,o2)->{
    
    
	o1.setTotal(o1.getTotal()+o2.getTotal());
	return o1;
})).valus().stream().collect(Collectors.toList());

expected outcome:

{
    
    "total":"15",
 "ways":[{
    
    "id":"1"}]
},
{
    
    "total":"3",
 "ways":[{
    
    "id":"2"}]
}

List(String) to List(Long) and other references: List collection type conversion