代碼訓練營——ArrayList

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要求：去除ArrayList集合中的重複元素

import java.util.*;class ArrayListTest{    public static void main(String[] args)    {        ArrayList al = new ArrayList();        al.add("1");        al.add("2");        al.add("1");        al.add("2");        al.add("1");        al.add("3");        al.add("4");        al.add("1");        sop(al);        ArrayList newAl = singleElement(al);        sop(newAl);        System.out.println("Hello world!");        //在迭代時迴圈中的next調用一次，就要hasNext判斷一次    }    public static ArrayList singleElement(ArrayList al)    {        ArrayList newAl = new ArrayList();        Iterator it = al.iterator();        while(it.hasNext())        {            Object obj = it.next();            if(!newAl.contains(obj))            {                newAl.add(obj);            }        }        return newAl;    }    public static void sop(Object obj)    {        System.out.println(obj);    }}

[1, 2, 1, 2, 1, 3, 4, 1]
[1, 2, 3, 4]
Hello world!

舉例：

//List集合判斷元素是否相同,依據是元素的equals方法import java.util.*;class Person{    private String name;    private int age;    Person(String name,int age)    {        this.name = name;        this.age = age;    }    public String getName()    {        return name;    }    public int getAge()    {        return 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;       }}

class ArrayListTest2    {        public static void sop(Object obj)        {            System.out.println(obj);        }        public static void main(String[] args)        {            ArrayList al = new ArrayList();            //al.add(Object obj);   Object obj = new Person("zhangsan",30);            al.add(new Person("zhangshan",20));            al.add(new Person("lisi",22));            al.add(new Person("wangwu",23));            al.add(new Person("wangwu",23));            al.add(new Person("alex",24));            al.add(new Person("alex",24));            al = singleElemenet(al);            sop("remove"+al.remove(new Person("alex",24)));            Iterator it = al.iterator();            while(it.hasNext())            {                Person p =(Person)it.next();                 sop(p.getName()+"::"+p.getAge());            }        }

public static ArrayList singleElemenet(ArrayList al)        {            ArrayList newAl = new ArrayList();            Iterator it = al.iterator();            while(it.hasNext())            {                Object obj = it.next();                if(!newAl.contains(obj))                {                    newAl.add(obj);                }            }            return newAl;        }

lisi……zhangshan
wangwu……zhangshan
wangwu……lisi
wangwu……zhangshan
wangwu……lisi
wangwu……wangwu
alex……zhangshan
alex……lisi
alex……wangwu
alex……zhangshan
alex……lisi
alex……wangwu
alex……alex
alex……zhangshan
alex……lisi
alex……wangwu
alex……alex
removetrue
zhangshan::20
lisi::22
wangwu::23

代碼訓練營——ArrayList