JAVA基础（ArrayList去除重复的自定义对象）

最新推荐文章于 2021-02-28 03:00:02 发布

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这篇博客讨论了如何在Java中从ArrayList中移除具有相同成员变量值的重复自定义对象。关键在于正确地重写equals()方法，因为contains()和remove()方法会依赖这个方法来判断对象是否相等。

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1，需求：ArrayList去除集合中自定义对象元素的重复值(对象的成员变量值相同

2，注意事项

重写equals()方法的
contains方法判断是否包含,底层依赖的是equals方法
remove方法判断是否删除,底层依赖的是equals方法


public class Demo2_ArrayList {



    public static void main(String[] args) {

        ArrayList list = new ArrayList();                //创建集合对象

        list.add(new Person("张三", 23));

        list.add(new Person("张三", 23));

        list.add(new Person("李四", 24));

        list.add(new Person("李四", 24));

        list.add(new Person("李四", 24));

        list.add(new Person("李四", 24));

        

        ArrayList newList = getSingle(list);            //调用方法去除重复

        System.out.println(newList);

        //list.remove(new Person("张三", 23));

        //System.out.println(list);

    }





    /*

     * 创建新集合将重复元素去掉

     * 1,明确返回值类型,返回ArrayList

     * 2,明确参数列表ArrayList

     *

     * 分析:

     * 1,创建新集合

     * 2,根据传入的集合(老集合)获取迭代器

     * 3,遍历老集合

     * 4,通过新集合判断是否包含老集合中的元素,如果包含就不添加,如果不包含就添加

     */

    public static ArrayList getSingle(ArrayList list) {

        ArrayList newList = new ArrayList<>();                    //1,创建新集合

        Iterator it = list.iterator();                            //2,根据传入的集合(老集合)获取迭代器

        

        while(it.hasNext()) {                                    //3,遍历老集合

            Object obj = it.next();                                //记录住每一个元素

            if(!newList.contains(obj)) {                        //如果新集合中不包含老集合中的元素

                newList.add(obj);                                //将该元素添加

            }

        }

        

        return newList;

    }

}

【2】bean

public class Person {

    private String name;

    private int age;

    public Person() {

        super();

        

    }

    public Person(String name, int age) {

        super();

        this.name = name;

        this.age = age;

    }

    

    

    @Override

    public int hashCode() {

        final int prime = 31;

        int result = 1;

        result = prime * result + age;

        result = prime * result + ((name == null) ? 0 : name.hashCode());

        return result;

    }

    @Override

    public boolean equals(Object obj) {

        if (this == obj)

            return true;

        if (obj == null)

            return false;

        if (getClass() != obj.getClass())

            return false;

        Person other = (Person) obj;

        if (age != other.age)

            return false;

        if (name == null) {

            if (other.name != null)

                return false;

        } else if (!name.equals(other.name))

            return false;

        return true;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public int getAge() {

        return age;

    }

    public void setAge(int age) {

        this.age = age;

    }

    @Override

    public String toString() {

        return "Person [name=" + name + ", age=" + age + "]";

    }

    /*@Override

    public boolean equals(Object obj) {

        Person p = (Person)obj;

        return this.name.equals(p.name) && this.age == p.age;

    }*/

    

}