list.addAll 与 for each 值变化 暂时没弄清楚怎么变的

package com.joyveb.test;

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

import com.joyveb.addon.common.domain.CoreSltoRecord;

public class ListTest {
??? public static void main(String[] args) {
??? ??? List<CoreSltoRecord> list = new ArrayList<CoreSltoRecord>();
??? ??? CoreSltoRecord c = new CoreSltoRecord();
??? ??? c.setIsvalid((short)1);
??? ??? list.add(c);
??? ???
??? ??? List<CoreSltoRecord> listall = new ArrayList<CoreSltoRecord>();
??? ??? listall.addAll(list);
??? ??? for(CoreSltoRecord r : list){
??? ??? ??? r.setIsvalid((short)2);
??? ??? }
//??? ??? for(CoreSltoRecord r : listall){
//??? ??? ??? r.setIsvalid((short)2);
//??? ??? }
??? ??? System.out.println(list.get(0).getIsvalid()); //值都是2
??? ??? System.out.println(listall.get(0).getIsvalid());//值都是2
??? }
}