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我对 Java 很陌生，这是我在大学的第二堂课（在大学里）使用它。在学期开始的时候，我做了一个简单的类来代表僵尸，其中包含他们的年龄、类型和名字。后来，我制作了一个整数链表。现在，我需要制作一个可以容纳这些“僵尸”的通用链表。我还必须制作一个菜单，允许我添加、删除、计数和显示“僵尸”。我已经盯着这个看了好几个小时，浏览了我的书，并在网上寻找我的问题的答案。我可以添加和显示这些“僵尸”，但在列表中计算它们并尝试删除它们只是告诉我输入的参数没有。换句话说，我如何比较“僵尸”可能存在问题。这是我的代码。我明白了'

僵尸.java

public class Zombie
{
private String zAge;
private String zType;
private String zName;

public Zombie(String zA, String zT, String zN)
{
    zAge = zA;
    zType = zT;
    zName = zN;
}

public void setZAge(String zA)
{
    zAge = zA;
}

public void setZType(String zT)
{
    zType = zT;
}

public void setZName(String zN)
{
    zName = zN;
}

public String getZAge()
{
    return zAge;
}

public String getZType()
{
    return zType;
}

public String getZName()
{
    return zName;
}

public boolean equals(Zombie zomb)
{
    if(zomb.getZAge() == zAge && zomb.getZType() == zType && zomb.getZName() == zName)
        return true;
    else
        return false;
}
}

LinkedBag.java

public class LinkedBag<E>
{
//Head node and number of nodes in bag
private Node<E> head;
private int manyNodes;

//Constructor
public LinkedBag()
{
    head = null;
    manyNodes = 0;
}

//Returns the number of nodes in the bag
public int getSize()
{
    return manyNodes;
}

//Returns the node that is at the head of the linked list
public Node<E> getListStart()
{
    return head;
}

//Adds a node to the beginning of the list
public void add(E element)
{
    head = new Node<E>(element,head);       //Creates a new node pointing to the head and sets the head of the linked bag to the new Node
    manyNodes++;        //Increments Node counter
}

//Counts the number of times Node [target] occurs within the bag
public int countOccurences(E target)
{
    int count = 0;      //Initializes incrementable counter

    if(head==null)      //Checks if bag is empty and returns null if bag is empty
        return 0;

    if(head.getData().equals(target))       //Checks if the head of the linked list is [target]
        count++;            //Increments counter

    Node<E> cursor = head;      //Sets temporary Node [cursor] to the same value and pointer as head

    while(cursor.getLink() != null)     //Loops until the next Node contains no value
    {
        if(cursor.getLink().getData().equals(target))           //Checks if the value of the next Node is [target]
            count++;                //Increments counter

        cursor=cursor.getLink();            //Cursor continues down linked list
    }

    return count;       //Returns incremented int [count], number of occurences of [target]
}

//Checks if Node [target] exists within the bag
public boolean exists(E target)
{
    if(head.getData().equals(target))       //Checks if the head of the linked list is [target]
        return true;

    Node<E> cursor = head;      //Sets temporary Node [cursor] to the same value and pointer as head

    while(cursor.getLink() != null)     //Loops until the next Node contains no value
    {
            if(cursor.getData().equals(target))     //Checks if current Node is [target] and returns true if true
                return true;

            cursor=cursor.getLink();        //Cursor continues down linked list
    }
            return false;       //Returns false if cursor goes through entire linked list and [target] isn't found
}

//Checks if Node [target] exists within the bag and removes the first occurence of it
public boolean remove(E target)
{       
    if(head==null)          //Returns false if bag is empty
        return false;

    if(head.getData().equals(target))   //If the head Node's data is [target]
    {
        head = head.getLink();      //Make the next Node the head
        manyNodes--;            //Decrements Node counter
        return true;            //Returns true, found [target]
    }

    Node<E> cursor = head;          //Sets temporary Node [cursor] to the same value and pointer as head

    while(cursor.getLink() != null)     //Loops until the next Node contains no value
    {
        cursor = cursor.getLink();      //Cursor continues down linked list

        if(cursor.getLink().getData().equals(target))   //If the next node's data is [target]
        {
            cursor.setLink(cursor.getLink().getLink());     //Sets current Node's link to the next Node's link, by passing the next Node
            manyNodes--;            //Decrements Node counter
            return true;            //Returns true, found [target]
        }
    }
    return false;           //Returns false, [target] not found
}
}

节点.java

public class Node<E>
{
private E data;
private Node<E> link;


public Node(E initialData, Node<E> initialLink)
{
    data = initialData;
    link = initialLink;
}

public E getData()
{
    return data;
}

public Node<E> getLink ()
{
    return link;
}

public void setData(E element)
{
    data = element;
}

public void setLink(Node<E> newLink)
{
    link = newLink;
}
}

这是用户与 ZombiesProj2.java 交互的菜单文件

import java.util.Scanner;

public class ZombiesProj2
{
public static void main(String[] args) throws InterruptedException
{
    LinkedBag<Zombie> zBag = new LinkedBag<Zombie>();       //Linked bag to hold Zombie Objects
    String choice = "";

    Scanner input = new Scanner(System.in);

    while(!choice.equalsIgnoreCase("x"))
    {   
        //Menu
        System.out.println("\nSac de Zombi\n");
        System.out.println("S - Display size of bag");
        System.out.println("A - Add 'Zombie' to bag");
        System.out.println("R - Remove 'Zombie' from bag");
        System.out.println("F - Find 'Zombie' in bag");
        System.out.println("D - Display contents of bag");
        System.out.println("X - Exit");
        System.out.print("Enter Selection: ");

        //Input and Output
        choice = input.nextLine();

        if(choice.equalsIgnoreCase("s"))
        {
            System.out.println("\nSize = " + zBag.getSize() + "\n");
        }
        else if(choice.equalsIgnoreCase("a"))       //adds zombie
        {
            String zAge;
            String zType;
            String zName;

            System.out.print("How many years has this zombie ROAMED THE EARTH: ");
            zAge = input.nextLine();
            System.out.print("What type of zombie is it: ");
            zType = input.nextLine();
            System.out.print("What would you like to name this zombie: ");
            zName = input.nextLine();

            Zombie newZomb = new Zombie(zAge,zType,zName);
            zBag.add(newZomb);
        }
        else if(choice.equalsIgnoreCase("r"))       //removes zombie
        {
            String zAge;
            String zType;
            String zName;

            System.out.print("How many years has this zombie ROAMED THE EARTH: ");
            zAge = input.nextLine();
            System.out.print("What type of zombie is it: ");
            zType = input.nextLine();
            System.out.print("What is the name of the zombie: ");
            zName = input.nextLine();

            Zombie rZomb = new Zombie(zAge,zType,zName);

            zBag.remove(rZomb);
        }
        else if(choice.equalsIgnoreCase("f"))       //counts number of matching zombies
        {
            String zAge;
            String zType;
            String zName;

            System.out.print("How many years has this zombie ROAMED THE EARTH: ");
            zAge = input.nextLine();
            System.out.print("What type of zombie is it: ");

            zType = input.nextLine();
            System.out.print("What is the name of the zombie: ");
            zName = input.nextLine();

            Zombie fZomb = new Zombie(zAge,zType,zName);

            System.out.println("The " + zAge + " year old zombie type " + zType + " named " + zName + " occurs " + zBag.countOccurences(fZomb)+ " time(s)");
        }
        else if(choice.equalsIgnoreCase("d"))       //displays entire zombie 'bag'
        {
            Node cursor = zBag.getListStart();
            Zombie dZomb;
            while(cursor !=null)
            {
                dZomb = (Zombie)cursor.getData();
                System.out.print("[Zombie "+dZomb.getZAge()+" "+dZomb.getZType()+" "+dZomb.getZName()+"],");
                cursor = cursor.getLink();
            }
        }
        else if(!choice.equalsIgnoreCase("x"))  
        {
            System.out.println("Error: Invalid Entry");
        }
    }
}
}

更新了 equals 和 hashCode

public boolean equals(Object obj)
{
    if(obj==null)
        return false;
    if(obj==this)
        return true;
    if(obj.getClass() != getClass())
        return false;

    Zombie zomb = (Zombie)obj;
    if(zomb.getZAge().equals(zAge) && zomb.getZType().equals(zType) && zomb.getZName().equals(zName))
        return true;
    else
        return false;
}

public int hashCode() { return 0; }
4

2 回答 2

3

我知道，因为您正在尝试学习编程，所以您正在编写自己的程序，linked list而不是使用 Java 的LinkedList. 但是，您错过了一些事情。

  1. 您的 equals 方法应该具有与Object Zombie.equals(Object). false而且，如果参数不是 Zombie ，它应该做的第一件事是返回。
  2. 每当你写一个equals方法时，你也必须写一个hashCode方法。查看大多数示例以获取详细信息。
  3. 永远不要对字符串使用等号运算符。始终使用 equals 方法。替换zomb.getZAge() == zAge为zomb.getZAge().equals(zAge)。
  4. 为什么zAge是一个String？你可以让它成为某种数字。
  5. 没有必要在课堂上到处都写“Z”。它在一个Zombie; 你的读者知道。在工作中，我有同事坚持在所有变量中重复类名。

这不是好的代码。

public class Document {
    private Long documentId;
    private String documentName;
    private String documentAuthor;
    private Date documentPublicationDate;
    // 10 more instance variables.
    // Constructors, accessors, other code.
}

然后他们将类型变量命名Document为documentA,documentB等。多么无聊、重复和多余。

于 2013-04-21T04:12:52.790 回答
0

1）你为什么要命名一个包含节点计数'manyNodes'而不是'nodeCount'的变量。如果你问一些随机的程序员，一个名为“manyNodes”的变量包含什么，你认为他们能猜到吗？如果你问一些随机的程序员 nodeCount 包含什么变量呢？您认为随机程序员甚至可以猜测 nodeCount 的类型吗？'manyNodes' 的类型呢？

2）如何尝试这样的事情：

public void add(Node<E> element)
{
    if (head == null) {
        head = element;
    }
    else {
        tail.nextNode = element;
    }

    tail = element;
    nodeCount++;        //Increments Node counter
}


public class Node<E>
{
    private E data;
    private Node<E> nextNode;
}


public class LinkedBag<E>
{

    private Node<E> head;
    private Node<E> tail;
    private int nodeCount;   
}

//Constructor
public LinkedBag()
{
    head = tail = null;
    nodeCount = 0;
}
于 2013-04-21T03:37:17.317 回答