在
Java 中实现
对象集合按
对象某个
属性去重，有多种方式，以下为几种常见实现示例：
### 方式一：使用
Java 8 流和 TreeSet
```
java
import
java.util.*;
import
java.util.stream.Collectors;
class Entity {
private String property;
public Entity
(String property
) {
this.property = property;
}
public String getProperty
() {
return property;
}
}
public class Main {
public static void main
(String[] args
) {
List<Entity> list = new ArrayList<>
();
list.add
(new Entity
("value1"
));
list.add
(new Entity
("value2"
));
list.add
(new Entity
("value1"
));
List<Entity> distinctList = list.stream
()
.distinct
()
.collect
(Collectors.collectingAndThen
(
Collectors.toCollection
(() -> new TreeSet<>
(Comparator.comparing
(Entity::getProperty
))),
ArrayList::new
));
distinctList.forEach
(entity -> System.out.println
(entity.getProperty
()));
}
}
```
此方法借助
Java 8 的流式编程和 `TreeSet` 达成按
属性去重，`TreeSet` 会依据指定
属性的比较器对元素进行排序并
去重，最后再将其转换为 `ArrayList` [^4]。
### 方式二：自定义
去重谓词（Predicate）
```
java
import
java.util.*;
import
java.util.function.Function;
import
java.util.function.Predicate;
class Player {
private String name;
private int age;
public Player
(String name, int age
) {
this.name = name;
this.age = age;
}
public String getName
() {
return name;
}
public int getAge
() {
return age;
}
@Override
public String toString
() {
return "Player{name='" + name + "', age=" + age + "}";
}
}
public class Main {
public static <T> Predicate<T> distinctByKey
(Function<? super T, ?> keyExtractor
) {
Set<Object> seen = ConcurrentHashMap.newKeySet
();
return t -> seen.add
(keyExtractor.apply
(t
));
}
public static void main
(String[] args
) {
List<Player> playerList = new ArrayList<>
();
playerList.add
(new Player
("Alice", 20
));
playerList.add
(new Player
("Bob", 25
));
playerList.add
(new Player
("Alice", 20
));
List<Player> distinctPlayers = playerList.stream
()
.filter
(distinctByKey
(Player::getName
))
.collect
(Collectors.toList
());
distinctPlayers.forEach
(System.out::println
);
}
}
```
此方法定义了一个通用的
去重谓词 `distinctByKey`，它利用 `ConcurrentHashMap.newKeySet
()` 来记录已出现的
属性值，进而实现
去重。该谓词可复用，适用于不同类型的
对象集合 [^5]。
### 方式三：使用 TreeSet 直接
去重
```
java
import
java.util.*;
class Player {
private String name;
private int age;
public Player
(String name, int age
) {
this.name = name;
this.age = age;
}
public String getName
() {
return name;
}
public int getAge
() {
return age;
}
@Override
public String toString
() {
return "Player{name='" + name + "', age=" + age + "}";
}
}
public class Main {
public static void main
(String[] args
) {
List<Player> playerList = new ArrayList<>
();
playerList.add
(new Player
("Alice", 20
));
playerList.add
(new Player
("Bob", 25
));
playerList.add
(new Player
("Alice", 20
));
Set<Player> playerSet = new TreeSet<>
(Comparator.comparing
(Player::getName
));
playerSet.addAll
(playerList
);
List<Player> distinctPlayers = new ArrayList<>
(playerSet
);
distinctPlayers.forEach
(System.out::println
);
}
}
```
此方法直接运用 `TreeSet` 和
属性比较器来对
集合进行
去重，`TreeSet` 会依据
属性比较器对元素进行排序并
去重，最后再转换为 `ArrayList` [^5]。
本文介绍了在Java中如何使用Stream API结合TreeSet实现对象列表的去重操作，具体包括根据用户年龄进行去重以及清空所有重复值的方法。示例代码展示了如何创建一个User对象列表，并通过比较User的age属性来达到去重目的。
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