java实用小技巧之判断list是否有重复项简单例子

//有一个list，里面是long类型的数字集合
List<Long> numbers = new ArrayList<>();
numbers.add(1L);
numbers.add(2L);
numbers.add(2L);
numbers.add(3L);
numbers.add(4L);
numbers.add(5L);
 
//判断里面是否有重复
DistinctUtil util = new DistinctUtil();
System.out.println(util.distinctList(numbers).size() == numbers.size());

public List<T> distinctList(List<T> rawList) {
    return rawList.stream().map(item -> item).distinct().collect(Collectors.toList());
}

@Data
@Builder
public class User {
    String name;
    Integer age;
}

public List<T> distinctComplexList(List<T> rawList, Function<? super T,?> mapLogic) {
    return (List<T>) rawList.stream().map(item -> mapLogic.apply(item)).distinct().collect(Collectors.toList());
}

//判断里面是否有重复
DistinctUtil<User> util = new DistinctUtil();
 
List<User> users = Arrays.asList(
        User.builder().name("鲁班七号").age(10).build(),
        User.builder().name("鲁班七号").age(10).build(),
        User.builder().name("安其拉").age(10).build()
);
 
Function<User, String> getName = User::getName;
System.out.println(util.distinctComplexList(users, User::getName ).size() == users.size());

public boolean isRepeat(List<T> rawList){
    return distinctList(rawList).size() < rawList.size();
}
 
public boolean isRepeat(List<T> rawList, Function<? super T,?> mapLogic){
    return distinctList(rawList).size() < rawList.size();
}

public static <T>  List<T> distinctList(List<T> rawList) {
    return rawList.stream().map(item -> item).distinct().collect(Collectors.toList());
}