定义一个功能将ArrayList 集合中的重复元素删除
ArrayList 集合中是允许储存重复元素的
import java.util.ArrayList;import java.util.Iterator;//定义一个功能将ArrayList 集合中的重复元素删除public class ArrayListDemes2 {public static void main(String[] args) {// 新建一个容器ArrayList a = new ArrayList();//调用自定义方法向集合中添加元素addelements(a);//调用自定义方法打印集合printArrayList(a);//ArrayList 中是可以添加重复元素的//调用自定义方法除集合中的重复元素System.out.println("————————————–");ArrayList a1 = removeRepeatElement(a);printArrayList(a1);}//自定义一个打印集合元素的方法private static void printArrayList(ArrayList a) {Iterator it = a.iterator();while(it.hasNext()){Studenti s = (Studenti)it.next();System.out.println(s.getName()+":"+s.getAge());}}//定义一个删除集合中重复元素的方法private static ArrayList removeRepeatElement(ArrayList a) {ArrayList al = new ArrayList();Iterator it = a.iterator();while(it.hasNext()){Studenti s = (Studenti) it.next();if(!(al.contains(s))){//contains 方法依靠的是equals 方法al.add(s);}}return al;}//定义向集合中添加元素的功能private static void addelements(ArrayList a) {a.add(new Studenti("kkk",22));a.add(new Studenti("sss",22));a.add(new Studenti("www",22));a.add(new Studenti("kkk",22));a.add(new Studenti("kkk",22));}}class Studenti{private String name;private int age;Studenti(String name ,int age){this.name=name;this.age = age;}public int getAge(){return age;}public String getName(){return name;}public String toString(){return "the student name : +name "+" and age is : "+ age;}public int hashCode(){return name.hashCode()+age*10;}public boolean equals(Object obj){ if(this == obj)return true ;//同一个对象放两次，，直接返回trueif(!(obj instanceof Studenti))throw new ClassCastException("类型错误");Studenti p = (Studenti)obj;return this .name.equals(p.name) && this.age == p.age;}}运行程序：
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