LinkedList对象如何使用Syso输出内容？

Question

我已经编写了一小段代码来实现链接列表数据结构。我有一个内部类“节点”，其中有两个字段“节点”和“值”。链表的构造方法接受int值参数，并将该值分配给Node对象，然后将Node对象添加到该LinkedList对象。

我的问题是java.util.LinkedList的哪个代码使列表对象被打印为数字列表，而不是其对象的地址？

当我打印“ list1”时，输出为[3,4]。当我打印“列表”时，输出是对象地址的哈希码。

我toString()在java.util.LinkedList课堂上没找到。

如何制作代码以打印LinkedList的内容？

下面是代码：

class LinkedList {

    Node first;

    Node getNode(){

        return new Node();

    }

    class Node{

        Node next;

        int value;

    }

    void add(int value){

        Node n=this.getNode();

        n.value=value;

        n.next=null;

        if (first==null){

            first=n;

        } else{

            first.next=n;

        }

    } 

}

public class LinkedListTest{

    public static void main(String[] args) {

        LinkedList list=new LinkedList();

        java.util.LinkedList<Integer> list1=new java.util.LinkedList<>();

        list1.add(3);

        list1.add(4);

        list.add(1);

        list.add(2);

        System.out.println(list);

        System.out.println(list1);

    }

}

Answer 1

您的类LinkedList（建议您重命名它，因为它可能与混淆java.util.LinkedList）需要重写method Object::toString，该方法在打印到控制台中被调用。我在java.util.LinkedList类中没有找到toString（）。有点侦探性的工作-您必须单击LinkedList<E>扩展的源代码，然后再扩展AbstractSequentialList<E>，AbstractList<E>最后扩展AbstractCollection<E>（源代码）类，在该类中，重写的Object::toString方法负责所有元素的类似于字符串的表示形式。在那里您可以得到启发。如何制作代码以打印LinkedList的内容？这条路：@Overridepublic String toString() {&nbsp; &nbsp; StringBuilder sb = new StringBuilder("[");&nbsp; &nbsp; if (first != null) {&nbsp; &nbsp; &nbsp; &nbsp; Node temp = first;&nbsp; &nbsp; &nbsp; &nbsp; String sep = "";&nbsp; &nbsp; &nbsp; &nbsp; while (temp != null) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; sb.append(sep).append(temp.value);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; temp = temp.next;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; sep = ", ";&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; return sb.append(']').toString();}

Answer 2

例如，您必须创建自己的toString方法class LinkedList {&nbsp; &nbsp; //...&nbsp; &nbsp; @Override&nbsp; &nbsp; public String toString() {&nbsp; &nbsp; &nbsp; &nbsp; StringBuilder text = new StringBuilder("[");&nbsp; &nbsp; &nbsp; &nbsp; String del = "";&nbsp; &nbsp; &nbsp; &nbsp; if (first != null) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; do {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; text.append(del).append(first.value);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; first = first.next;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; del = ", ";&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; } while (first != null);&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; text.append(']');&nbsp; &nbsp; &nbsp; &nbsp; return text.toString();&nbsp; &nbsp; }}如果再次运行代码，则输出[1, 2]