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public class Test {
public static void main(String[] args) {
Product product1 = new Product("type1", "name1");
Product product2 = new Product("type1", "name2");
Product product3 = new Product("type2", "name2");
Product product4 = new Product("type3", "name3");
List<Product> list = new ArrayList<>();
list.addAll(Arrays.asList(product1,product2,product3,product4));
Map<String, List<String>> result = list.stream()
.collect(Collectors.toMap(p -> p.getType(), p -> Collections.singletonList(p.getName()),
(existValue,newValue)-> {
List<String> r = new ArrayList<>(existValue);
r.addAll(newValue);
return r;
}));
System.out.println(result);
}
}
@Data
@AllArgsConstructor
class Product {
String type;
String name;
}
输出结果如下:
{type3=[name3], type2=[name2], type1=[name1, name2]}