java集合值在所有列表变量中都得到更新

Question

我有一个复杂的结构，比如

ArrayList<LinkedList<Struct>>

在我的主类中，我有两个嵌套类，如下所示

  static class struct {

            private String name;
            Set<String> rights = new HashSet<String>();
//getters and setters
    }
    static class Graph {
            ArrayList<LinkedList<struct>> adjListArray;

            Graph() {
                adjListArray = new ArrayList<>();
            }
        }

加法函数

    static void addEdge(Graph graph, String src, String dest, Set<String> rights) {
// code for creating a src block if it is not present and adding dest to it as below
    struct destStruct = new struct();
            destStruct.setName(dest);
            destStruct.setRights(rights);
            graph.adjListArray.get(getIndexOf(graph, src)).add(destStruct); // getIndexof is a function which will return the list index whose first element name is equal to src
    }

我从主函数传递这些值

public static void main(String args[]) {
        Graph graph = new Graph();
        Set<String> rights = new HashSet<String>();
        rights.add("T");
        rights.add("G");
        addEdge(graph, "A", "V", rights);
        rights.clear();
        rights.add("G");
        addEdge(graph, "B", "V", rights);
        printGraph(graph);
}

打印图函数

static void printGraph(Graph graph) {
        for (LinkedList<struct> list : graph.adjListArray) {
            for (struct var : list) {
                System.out.println(
                        "src=" + list.get(0).getName() + " dest=" + var.getName() + " rights=" + var.getRights());
            }
            System.out.println("\n");
        }
    }

输出是

src=A dest=A rights=[]
src=A dest=V rights=[G]


src=B dest=B rights=[]
src=B dest=V rights=[G]

但预期产出是有限的

src=A dest=A rights=[]
src=A dest=V rights=[T, G]


src=B dest=B rights=[]
src=B dest=V rights=[G]

我不明白为什么边缘的权利（A，V）被更新为（B，V）的权利。当我只从main发送（A，V）时，我得到的值是正确的

src=A dest=A rights=[]
src=A dest=V rights=[T, G]

想了解为什么会发生这种情况，以及如何解决

Answer 1

列表。清除（）

clear（）将遍历底层数组，并将每个条目设置为null

使用rights.clear()删除了指向以下内容的引用：

rights.add("T");        
rights.add("G");

在图形中，您必须为更改创建一个新的权限副本，否则使用clear()将从内存中删除所有现有引用

更新addEdge方法：-

static void addEdge(Graph graph, String src, String dest, Set<String> rights) {
           Set<String> copyRights = new HashSet<>(rights); //create a new copy of rights.
            struct destStruct = new struct();
                    destStruct.setName(dest);
                    destStruct.setRights(copyRights);
                    graph.adjListArray.get(getIndexOf(graph, src)).add(destStruct); // getIndexof is a function which will return the list index whose first element name is equal to src
}