ArrayList使用

ArrayList

ArrayList继承了AbstractList，实现了List,Serializable等接口。它内部实现是是基于数组的。
List的实现类的clone都是浅复制：如果只是remove,就不会影响到浅复制的应用，修改会影响
add的时候当前长度大于数组长度就会扩容数组，把当前的数组内容拷贝到新数组然后重新 引用。
ArrayList可以转为数组，最好的方法是就是ublic T[] toArray(T[] a)，安全！

例子

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.extern.slf4j.Slf4j;

@Slf4j
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Pet{
    private String name;
}

import java.util.ArrayList;
import java.util.List;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.extern.slf4j.Slf4j;

@Slf4j
@Data
public class Pets{
    public static List<Pet> getPets(){
        List<Pet> list=new ArrayList<Pet>();
        Pet petdog=new Pet("dog");
        Pet petpig=new Pet("pig");
        Pet petxiaoji=new Pet("xiaoji");
        list.add(petdog);
        list.add(petpig);
        list.add(petxiaoji);
        return list;
    }
}

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

import lombok.extern.slf4j.Slf4j;

@Slf4j
public class ArrayListTest {
    public static void main(String[] args) {
        ArrayList<Pet> list=new ArrayList<Pet>();
  
        //add all
        list.addAll(Pets.getPets());
        log.info("list size{}",list.size());
        //contains
        log.info("contain obj");
        for(Pet pet:list){
            if(list.contains(pet)){
                log.info("{}:{}",pet.toString(),list.indexOf(pet));
            }
        }
        //remove

        // iterator
        log.info("iterator list");
        Iterator<Pet> it=list.iterator();
        while(it.hasNext()){
            log.info(it.next().toString());
        }
        //foreach
        log.info("Foreach list");
        for(Pet pet:list){
            log.info(pet.toString());
        }
        //to Array
        Pet[]pets=list.toArray(new Pet[0]);
        log.info("ToArray");
        for(Pet pet:pets){
            log.info(pet.toString());
        }
        //Array to List
        List<Pet> list2=Arrays.asList(pets);
        log.info("array to list");
        for(Pet pet:list2){
            log.info(pet.toString());
        }
        //contain
        log.info("contains object");
        for(Pet pet:list){
            if(list2.contains(pet)){
                log.info("{}:{}",pet.toString(),list2.indexOf(pet));
            }
        }
        //contain all
        log.info("contain all");
        if(list2.containsAll(list)){
            log.info("list2 contain list");
        }
        //clone 浅复制
        ArrayList<Pet> list3=(ArrayList)list.clone();
        log.info(list3.toString());

        list.get(2).setName("reset xiaoji");
        log.info(list3.toString());
        //remove
        //remove all
        log.info("Removeall list");
        list.removeAll(list);
        list.clear();
        for(Pet pet:list){
            log.info(pet.toString());
        }
        

输出

2019-07-11 21:23:28,321   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - list size3
2019-07-11 21:23:28,326   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - contain obj
2019-07-11 21:23:28,327   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=dog):0
2019-07-11 21:23:28,327   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=pig):1
2019-07-11 21:23:28,327   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=xiaoji):2
2019-07-11 21:23:28,327   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - iterator list
2019-07-11 21:23:28,327   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=dog)
2019-07-11 21:23:28,327   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=pig)
2019-07-11 21:23:28,327   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=xiaoji)
2019-07-11 21:23:28,327   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Foreach list
2019-07-11 21:23:28,328   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=dog)
2019-07-11 21:23:28,328   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=pig)
2019-07-11 21:23:28,328   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=xiaoji)
2019-07-11 21:23:28,328   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - ToArray
2019-07-11 21:23:28,328   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=dog)
2019-07-11 21:23:28,328   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=pig)
2019-07-11 21:23:28,328   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=xiaoji)
2019-07-11 21:23:28,328   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - array to list
2019-07-11 21:23:28,329   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=dog)
2019-07-11 21:23:28,329   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=pig)
2019-07-11 21:23:28,329   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=xiaoji)
2019-07-11 21:23:28,329   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - contains object
2019-07-11 21:23:28,329   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=dog):0
2019-07-11 21:23:28,329   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=pig):1
2019-07-11 21:23:28,329   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Pet(name=xiaoji):2
2019-07-11 21:23:28,329   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - contain all
2019-07-11 21:23:28,329   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - list2 contain list
2019-07-11 21:23:28,330   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - [Pet(name=dog), Pet(name=pig), Pet(name=xiaoji)]
2019-07-11 21:23:28,330   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - [Pet(name=dog), Pet(name=pig), Pet(name=reset xiaoji)]
2019-07-11 21:23:28,330   [main] INFO  com.fang.java.javabase.firstcollection.ArrayListTest  - Removeall list