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,我创建了一个简单的类来表示僵尸,其中包含它们的年龄、类型和名称。后来,我做了一个整数链表。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”。我已经盯着它看了好几个小时,翻阅我的书,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,我比较“僵尸”的方式可能有问题。这是我的代码。我知道这是一个很好的 300 行代码来浏览......但我没有想法。
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;
}
}
这是用户与之交互的菜单文件 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");
}
}
}
}
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; }
最佳答案
我知道,因为您正在尝试学习编程,所以您正在编写自己的链表
,而不是使用 Java 的 LinkedList
。但是,您错过了一些事情。
- 您的 equals 方法应该与
Object
Zombie.equals(Object)
中的签名相同。而且,如果参数不是 Zombie,它应该做的第一件事是返回false
。 - 无论何时编写 equals 方法,都必须同时编写 hashCode 方法。查看大多数示例以了解详细信息。
- 切勿对字符串使用等于运算符。始终使用 equals 方法。将
zomb.getZAge() == zAge
替换为zomb.getZAge().equals(zAge)
。 - 为什么 zAge 是一个
String
?你可以让它成为某种数字。 - 没必要在你的类里面到处写“Z”。它在
僵尸
中;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 Document
类型的变量命名为 documentA
、documentB
等。多么无聊、重复和多余。
关于java - 通用对象链表 (Java),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/16127554/