List 的add/addall 方法

1. 当list = list的时候，仅仅是地址的复制，如果修改其中一个list必定改变另外一个list
2. 当list.addall(list)的时候，只是一个浅复制，如果只是remove，和1不同的是另一个list不会改变（对于基本类型而言），当类型是类的话，如果对象的属性改变了，另一个list也会改变
3. List<List>类型的用add方法时，如果<>里面的List改变了就会导致List<List>改变

public static void main(String[] args){
        List<Integer> integerList = new ArrayList<>();
        integerList.add(1);
        integerList.add(2);
        integerList.add(3);
        List<Integer> integerList1 = new ArrayList<>();
        integerList1 = integerList;
        integerList.remove(0);
        System.out.println("integerList:"+integerList);
        System.out.println("integerList1:"+integerList1);
        //integerList:[2, 3]
        //integerList1:[2, 3]
        List<Integer> integerList2 = new ArrayList<>();
        integerList2.addAll(integerList);
        integerList.remove(0);
        System.out.println("integerList:"+integerList);
        System.out.println("integerList2"+integerList2);
        //integerList:[3]
        //integerList2[2, 3]
        List<ListNode> listNodes = new ArrayList<>();
        listNodes.add(new ListNode(1));
        listNodes.add(new ListNode(2));
        listNodes.add(new ListNode(3));
        List<ListNode> listNodes1 = new ArrayList<>();
        listNodes1.addAll(listNodes);
        listNodes.get(0).setVal(4);
        System.out.println("listNodes:"+listNodes);
        System.out.println("listNodes1:"+listNodes1);
        //listNodes:[ListNode{val=4, next=null}, ListNode{val=2, next=null}, ListNode{val=3, next=null}]
        //listNodes1:[ListNode{val=4, next=null}, ListNode{val=2, next=null}, ListNode{val=3, next=null}]
        listNodes.remove(0);
        System.out.println("listNodes:"+listNodes);
        System.out.println("listNodes1:"+listNodes1);
        //listNodes:[ListNode{val=2, next=null}, ListNode{val=3, next=null}]
        //listNodes1:[ListNode{val=4, next=null}, ListNode{val=2, next=null}, ListNode{val=3, next=null}]
        List<List<Integer>> lists = new ArrayList<>();
        lists.add(integerList);
        System.out.println("lists:"+lists);
        System.out.println("integerList:"+integerList);
        //lists:[[3]]
        //integerList:[3]
        integerList.clear();
        System.out.println("lists:"+lists);
        System.out.println("integerList:"+integerList);
        //lists:[[]]
        //integerList:[]
    }