（TL; DR：跳到粗体。）
我正在尝试为修改后的九头蛇建立计算机模拟-在此版本中，每个九头蛇头都可以有更多的九头蛇头出来。我认为这非常类似于节点，因此我首先构建了一个通用的Node类。每个Node对象都有一个ArrayList<Node> children，每个（也都是Node）都可以有自己的children。
九头蛇的头的结构与Node相同，但行为不同。 （例如，一个Node应该能够简单地删除其子对象，而从九头蛇中删除一个头部也需要重新生成一些头部。）因此，我构建了HydraNode extends Node并添加了cutHead()这样的方法（该方法删除了一个头部（节点），然后添加克隆）。 Hydra是“身体”，头部带有HydraNode。
问题是，因为所有子节点都存储为ArrayList<Node>，所以我可以
Hydra hydra = new Hydra(1,1,1) // Makes a Hydra with 3 levels (1 head, which has 1 head, which has 1 head).
Node nodeAtLevel1 = hydra.getChildren.get(0); // Has to be declared as Node, not HydraNode, because getChildren() is a Node method, and returns an ArrayList<Node> of children.
，但其每个子级实际上都是节点。这会导致
main()中的问题，我尝试在其中运行nodeAtLevel1.cutHead()但不能，因为cutHead()是HydraNode方法。在对象包含自身的情况下，如何为类添加功能？将对象扩展为
subclass似乎不起作用，因为检索包含的对象将返回superclass类型的对象，而不是subclass类型的对象。而且我不能把它往下扔。我能做什么？节点java
public class Node {
// Member variables
private ArrayList<Node> children = new ArrayList<>(); // Holds "children" nodes.
private int hierarchyLevel; // Where in the hierarchy is it?
private int childCount = 0; //How many "child" nodes does this node have?
// Constructors
public Node(int hierarchyLevel) {this.hierarchyLevel = hierarchyLevel}
public Node(int hierarchyLevel, int... nodesPerLevel) {this(hierarchyLevel;} //Adds children to this node, eg. {1,2,1} adds 1 child node at lvl 1, 2 children at lvl 2, each with 1 child of their own at level 3.
// Methods
public ArrayList<Node> getChildren() {return children;}
public void addChild() {} // Adds a child directly to this node
public void removeChild(int i) {}
public Node getCopy() {} //Returns a clone of this Node and all its child nodes.
public String toString() {} // Eg. Node at Level ___ has ____ children.
}
HydraNode.java（负责人）
public class HydraNode extends Node {
// Constructors
public HydraNode(int hierarchyLevel) { // Just call super, bc this is essentially a Node structure that just acts a little differently.
super(hierarchyLevel);
}
public HydraNode(int hierarchyLevel, int... nodesPerLevel) {
super(hierarchyLevel, nodesPerLevel);
// Methods
public void cutHead() {} // Cutting a Level 1 head, which is attached to the body (level 0), does not regrow. However, any other cut will multiply that branch's parent x3.
}
Hydra.java
public class Hydra {
// MAIN method
public static void main(String[] args) {
Hydra hydra = new Hydra(1,1,1);
Node head2 = hydra.body.getChildren().get(0).getChildren().get(0);
System.out.println(head2.toString()); // >> Node at Level 2 has 1 child node.
//head2.cutHead(); // Doesn't work because cutHead() is a HydraNode method, not a Node method.
}
// Member Variables
public static int regrowFactor = 2; // Every time a head is cut off, the hydra clones the remaining branches. In the original video, the hydra forms two new clones.
HydraNode body;
// Constructors
public Hydra() {
body = new HydraNode(0); // the body is just a new Node at level 0
}
public Hydra(int... headsPerLevel) {
body = new HydraNode(0, headsPerLevel);
}
}
最佳答案
我们所有的强制转换建议都失败了，因为：
public HydraNode(int hierarchyLevel, int... nodesPerLevel) {
super(hierarchyLevel, nodesPerLevel);
从Hydra构造HydraNode时，您正在调用
super()构造函数将其链接。这意味着您最终得到：HydraNode -> Node -> Node您应该打电话给：
this(hierarchyLevel, nodesPerLevel);
因此，创建链始终会产生更多的HydraNode。
HydraNode -> HydraNode -> HydraNode然后，您将能够从Node-> HydraNode进行投射，并按照许多响应中的指定调用
cutHead。关于java - 试图通过在子类中扩展方法来向类添加方法？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/46799728/