Java Lambda表达式对象集合交集，差集，去重

1、第一种

//从数据库取的数据
List<User> saleTaskItemOldList = new ArrayList<>();
 
//从前端修改的数据
List<User> saleTaskItemNewList = new ArrayList<>();
 
//修改的
List<User> updateOldList = saleTaskItemNewList.stream()
                            .filter(item -> saleTaskItemOldList.stream()
                            .map(e -> e.getName())
                            .collect(Collectors.toList())
                            .contains(item.getName()))
                            .collect(Collectors.toList());
 
//删除的
List<User> deleteOldList = saleTaskItemOldList.stream()
                            .filter(item -> !saleTaskItemNewList.stream()
                            .map(e -> e.getName())
                            .collect(Collectors.toList())
                            .contains(item.getName()))
                            .collect(Collectors.toList());
 
//新的
List<User> newList = saleTaskItemNewList.stream()
                            .filter(item -> !saleTaskItemOldList.stream()
                            .map(e -> e.getName())
                            .collect(Collectors.toList())
                            .contains(item.getName()))
                            .collect(Collectors.toList());

//交集
List<User> sameList = saleTaskItemNewList.stream()
							.filter(u1-> saleTaskItemOldList.contains(u1))
							.collect(Collectors.toList());

//去重
List<User> userList = list1.stream()
		.collect(Collectors.collectingAndThen(
		Collectors.toCollection(() -> new TreeSet<>(
		Comparator.comparing(user -> user.getName()))), ArrayList::new));

2、第二种

//从数据库取的数据
List<User> saleTaskItemOldList = new ArrayList<>();
 
//从前端修改的数据
List<User> saleTaskItemNewList = new ArrayList<>();
 
//修改的
List<User> updateOldList = saleTaskItemNewList.stream()
							.filter(u1-> saleTaskItemOldList.contains(u1))
							.collect(Collectors.toList());
 
//删除的
List<User> deleteOldList = saleTaskItemOldList.stream()
							.filter(u1-> !saleTaskItemNewList.contains(u1))
							.collect(Collectors.toList());
 
//新的
List<User> newList = saleTaskItemNewList.stream()
							.filter(u1-> !saleTaskItemOldList.contains(u1))
							.collect(Collectors.toList());

总结：使用对象中的属性比较精确，直接使用对象本身也是没问题的。