Java中List集合里Contains和Remove方法的本质

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Java中List集合里的Contains和Remove方法里都会调用Equals()方法，所以如果要判断两个集合中是否包含相同对象，或者从一个集合中删除一个具体的对象，需要在对象类中重写Equals()方法，例如如下实例：

import java.util.*;/*将自定义对象作为元素存到ArrayList集合中，并去除重复元素。比如：存人对象。同姓名同年龄，视为同一个人。为重复元素。思路：1，对人描述，将数据封装进人对象。2，定义容器，将人存入。3，取出。List集合判断元素是否相同，依据是元素的equals方法。*/class Person{private String name;private int age;Person(String name,int age){this.name = name;this.age = age;}<strong><span style="color:#ff0000;">public boolean equals(Object obj){if(!(obj instanceof Person))return false;Person p = (Person)obj;//System.out.println(this.name+"....."+p.name);return this.name.equals(p.name) && this.age == p.age;}</span></strong>public String getName(){return name;}public int getAge(){return age;}}class ArrayListTest2 {public static void sop(Object obj){System.out.println(obj);}public static void main(String[] args) {ArrayList al = new ArrayList();al.add(new Demo());al.add(new Person("lisi01",30));   //al.add(Object obj);//Object obj = new Person("lisi01",30);al.add(new Person("lisi02",32));al.add(new Person("lisi02",32));al.add(new Person("lisi04",35));al.add(new Person("lisi03",33));al.add(new Person("lisi04",35));//al = singleElement(al);sop("remove 03 :"+al.remove(new Person("lisi03",33)));//remove方法底层也是依赖于元素的equals方法。Iterator it = al.iterator();while(it.hasNext()){Person p = (Person)it.next();sop(p.getName()+"::"+p.getAge());}}public static ArrayList singleElement(ArrayList al){//定义一个临时容器。ArrayList newAl = new ArrayList();Iterator it = al.iterator();while(it.hasNext()){Object obj = it.next();if(!newAl.contains(obj))newAl.add(obj);}return newAl;}}

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