通用链接对象列表（Java）(Generic Linked List of Objects (Java))

 我是Java的新手，这是我使用它的第二堂课（在大学里）。 在学期开始时，我创建了一个代表Zombies的简单类，它包含了它们的年龄，类型和名称。 后来，我制作了一个整数链表。 现在，我需要创建一个可以容纳这些“Zombies”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'Zombies'。 我一直盯着这几个小时，浏览我的书，并在网上寻找我的问题的答案。 我可以添加并显示这些'Zombies'，但是在列表中计算它们并尝试删除它们只是让它告诉我没有我输入的参数。 换句话说，我可能会比较“僵尸”的问题。 这是我的代码。 我理解这是一个很好的300行代码来查看...但我没有想法。 
 
 Zombie.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
}
}
 
 Node.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; }

I'm pretty new to Java, with this being my second class (in College) using it. Towards the beginning of the semester, I made a simple class representing Zombies that holds their age, type, and name. Later on, I made a linked list of integers. Now, I need to make a generic linked list that can hold these 'Zombies'. I also have to make a menu that allows me to add, remove, count, and display 'Zombies'. I've been staring at this for hours, going through my book, and looking online for the answer to my problem. I can add and display these 'Zombies', but counting them in the list and trying to remove them simply has it tell me there's none with the parameters I entered. In other words, there might be a problem with how I compare the 'Zombies'. Here's my code. I understand it's a good 300 lines of code to look through... but i'm out of ideas.
 
Zombie.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
}
}
 
Node.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;
}
}
 
And this is the menu file that the user interacts with ZombiesProj2.java
 
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");
        }
    }
}
}
 
Updated equals and 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; }

原文：https://stackoverflow.com/questions/16127554