ArrayList复制问题，arraylist复制

ArrayList复制问题，arraylist复制

代码

package S;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;


public class T802 {
    public static void main(String[] args) {
        ArrayList<Stu> rawArrayList=new ArrayList<Stu>();
        for (int i = 0; i <6; i++) {
            Stu ssStu=new Stu();
            ssStu.type=i;
            ssStu.url="http://url/"+i+"jpg";
            rawArrayList.add(ssStu);
        }
        System.out.println(rawArrayList);

        System.out.println("-------new ArrayList<Stu>(rawArrayList)-----");
        ArrayList<Stu> newArrayList=new ArrayList<Stu>(rawArrayList);
        int dex=0;
        Stu  stu1=newArrayList.get(dex);
        stu1.url=stu1.url+"---new ArrayList<Stu>(rawArrayList)----";
        newArrayList.set(dex, stu1);
        System.out.println(newArrayList);
        System.out.println("-----ArrayList2修改是否影响ArrayList1---");
        System.out.println(rawArrayList);
        System.out.println(newArrayList);
        System.out.println(newArrayList==rawArrayList);

        System.out.println("-------尝试克隆-----");
        ArrayList<Stu> cloneArrayList=(ArrayList<Stu>) rawArrayList.clone();
        System.out.println(cloneArrayList);
        int dex2=1;
        Stu  stu2=cloneArrayList.get(dex2);
        stu2.url=stu2.url+"===rawArrayList.clone()=====clone====";
        cloneArrayList.set(dex2, stu2);
        System.out.println("-----clone的ArrayList修改是否影响原来的ArrayList---");
        System.out.println(rawArrayList);
        System.out.println(cloneArrayList);
        System.out.println(cloneArrayList==rawArrayList);






        System.out.println("-------尝试一个一个元素复制-----");
        ArrayList<Stu> anotherArrayList=new ArrayList<Stu>();
        for (int i = 0; i < rawArrayList.size(); i++) {
            anotherArrayList.add(rawArrayList.get(i));
        }
        System.out.println(anotherArrayList);
        int dex3=2;
        Stu  stu3=anotherArrayList.get(dex3);
        stu3.url=stu3.url+"===一个一个元素复制====";
        anotherArrayList.set(dex3, stu3);
        System.out.println("-----一个一个元素复制---修改是否影响原来的ArrayList---");
        System.out.println(rawArrayList);
        System.out.println(anotherArrayList);
        System.out.println(anotherArrayList==rawArrayList);

        System.out.println("-------尝试一个一个元素复制--只复制简单数据---");
        ArrayList<Stu> copyArrayList=new ArrayList<Stu>();
        for (int i = 0; i < rawArrayList.size(); i++) {
            Stu stu=rawArrayList.get(i);
            Stu stuCopy=new Stu();
            stuCopy.url=stu.url;
            stuCopy.type=stu.type;
            copyArrayList.add(stuCopy);
        }
        System.out.println(copyArrayList);
        int dex4=3;
        Stu  stu4=copyArrayList.get(dex4);
        stu4.url=stu4.url+"--------只复制简单数据---";
        copyArrayList.set(dex4, stu4);
        System.out.println("-----只复制简单数据---修改是否影响原来的ArrayList---");
        System.out.println(rawArrayList);
        System.out.println(copyArrayList);
        System.out.println(copyArrayList==rawArrayList);




        System.out.println("-------先new后尝试克隆-----");
        ArrayList<Stu> newcloneArrayList=new ArrayList<Stu>();
        newcloneArrayList=(ArrayList<Stu>) rawArrayList.clone();
        System.out.println(newcloneArrayList);
        int dex5=4;
        Stu  stu5=newcloneArrayList.get(dex5);
        stu5.url=stu5.url+"==---先new后尝试克隆--====";
        newcloneArrayList.set(dex5, stu5);
        System.out.println("-----先new后尝试克隆---是否影响原来的ArrayList---");
        System.out.println(rawArrayList);
        System.out.println(newcloneArrayList);
        System.out.println(newcloneArrayList==rawArrayList);


        try {
            System.out.println("-------deepCopy-----");
            ArrayList<Stu> deepCopyArrayList=(ArrayList<Stu>) deepCopy(rawArrayList);
            System.out.println(deepCopyArrayList);
            int dex6=5;
            Stu  stu6=deepCopyArrayList.get(dex6);
            stu6.url=stu6.url+"==---deepCopy-====";
            deepCopyArrayList.set(dex6, stu6);
            System.out.println("-----deepCopy---是否影响原来的ArrayList---");
            System.out.println(rawArrayList);
            System.out.println(deepCopyArrayList);
            System.out.println(deepCopyArrayList==rawArrayList);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }


    //使用深拷贝是对象必须是 implements Serializable
    //否则java.io.NotSerializableException: S.Stu

    public static <T> List<T> deepCopy(List<T> src) throws Exception{  
        ByteArrayOutputStream byteOut = new ByteArrayOutputStream();  
        ObjectOutputStream out = new ObjectOutputStream(byteOut);  
        out.writeObject(src);  

        ByteArrayInputStream byteIn = new ByteArrayInputStream(byteOut.toByteArray());  
        ObjectInputStream in = new ObjectInputStream(byteIn);  
        @SuppressWarnings("unchecked")  
        List<T> dest = (List<T>) in.readObject();  
        return dest;  
    } 
}
class Stu implements Serializable{
    //    type  int 广告类型
     int type;

    //    url   String  广告展示的图片地址或者视频地址或者网页地址
     String url;

    @Override
    public String toString() {
        return "Stu [type=" + type + ", url=" + url + "]";
    }

}

分析

只有简单复制元素或者深拷贝时才不会影响到原来的ArrayList

可以参考这个分析
http://blog.csdn.net/demonliuhui/article/details/54572908

//使用深拷贝是对象必须是 implements Serializable
//否则java.io.NotSerializableException: S.Stu