集合框架_05_ArrayList集合

来源：互联网发布：神优化单机游戏低配编辑：程序博客网时间：2024/06/05 17:02

一、去除ArrayList中的重复

/*去除ArrayList集合中的重复元素。*/class ArrayListTest {public static void sop(Object obj){System.out.println(obj);}public static void main(String[] args) {ArrayList al = new ArrayList();al.add("java01");al.add("java02");al.add("java01");al.add("java02");al.add("java01");//al.add("java03");/*在迭代时循环中next调用一次，就要hasNext判断一次。Iterator it = al.iterator();while(it.hasNext()){sop(it.next()+"...."+it.next());}*//**/sop(al);al = singleElement(al);sop(al);}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;}}

二、将自定义对象作为元素存到ArrayList集合中，并去除重复元素

/* 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;}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;}/**/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 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;}}

0 0