Java List<Object>去掉重复对象

两个list去重，

如果list里面都是基础对象的话，直接去重就好了

list1.removeAll(list2);

list2.addAll(list1);

但是如果list里面是对象的话，我们就要考虑重写list比较的方法了，list用的是equals，思路如下：

Person类

public class Person {    private Long id;    private String name;    public Person(Long id, String name) {        this.id = id;        this.name = name;    }    public Long getId() {        return id;    }    public void setId(Long id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    @Override    public String toString() {        return "Person{" +                "id=" + id +                ", name='" + name + '\'' +                '}';    }}

重写Person对象的equals()方法和hashCode()方法:

 @Override    public boolean equals(Object o) {        if (this == o) return true;        if (o == null || getClass() != o.getClass()) return false;        Person person = (Person) o;        if (!id.equals(person.id)) return false;        return name.equals(person.name);    }    @Override    public int hashCode() {        int result = id.hashCode();        result = 31 * result + name.hashCode();        return result;    }

下面对象去重的代码：

Person p1 = new Person(1l, "jack");        Person p2 = new Person(3l, "jack chou");        Person p3 = new Person(2l, "tom");        Person p4 = new Person(4l, "hanson");        Person p5 = new Person(5l, "胶布虫");        List<Person> persons = Arrays.asList(p1, p2, p3, p4, p5, p5, p1, p2, p2);        List<Person> personList = new ArrayList<>();        // 去重        persons.stream().forEach(                p -> {                    if (!personList.contains(p)) {                        personList.add(p);                    }                }        );        System.out.println(personList);

List 的contains()方法底层实现使用对象的equals方法去比较的，其实重写equals()就好，但重写了equals最好将hashCode也重写了。

可以参见:http://stackoverflow.com/questions/30745048/how-to-remove-duplicate-objects-from-java-arraylist 
http://blog.csdn.net/growing_tree/article/details/46622579