访问 ArrayList 中的特定元素

Question

我正在创建一个程序来将客人添加到聚会中。来宾的最大数量设置为 3。我的程序正确输出了 3 位来宾。

但是，如何访问并打印出没有出现在列表中的元素？

如您在我的 Party2Driver 中所见，我调用了 "addGuest" 方法 5 次。由于我将 maxGuests 设置为 3，程序正确地将前 3 个名字添加到列表中。但是如何输出未添加到列表中的最后两个名字？

我希望它显示类似 "blank and blank" 的内容，因为来宾列表已满，所以未添加到列表中。

每次我尝试使用 "get method" 访问那些 ArrrayList 元素时，它都会抛出 OutOutBoundException。

感谢任何帮助！

import java.util.ArrayList;

public class Party2Driver
{
 public static void main(String[] args)
    {

      Party2 party = new Party2(3, "David Beckham");
      party.addGuest("Roberto Baggio");
      party.addGuest("Zinedine Zidane");
      party.addGuest("Roberto Baggio");
      party.addGuest("Johan Cruyff");
      party.addGuest("Diego Maradona");
      party.printParty();

    } // end main

}//end Party2Driver

这是派对 2 Class 我的方法：

import java.util.ArrayList;

public class Party2
{
    // instance variables that will hold your data
    // private indicates they belong to this class exclusively
    private int maxGuests;
    private String host;
    private ArrayList<String> guests;

    //Constructor
    public Party2(int maxGuests, String host)
    {
        System.out.println("Maximum number of guests: " + maxGuests + ".  Guest list for " + host + "'s party. \n");
        this.guests = new ArrayList<String>();
        this.maxGuests = maxGuests;
        this.host = host;
    }

    //getter
    // define type of data to be returned
    public String getHost()
    {
        System.out.println("Setting host to: " + host);
        return host;
    }

    //setter
    // setters have type void b/c they return nothing
    public void setHost(String host)
    {
        System.out.println("Setting host to: " + host);
        this.host = host;
    }

    //*************************************
    //Method to add to guest list
    public void addGuest(String guest)
    {

        if (guests.size() < maxGuests)
        {
            System.out.println("Guest: " + guest + "\n");
            this.guests.add(guest);
        }

        else
        {
            System.out.println("     Guest cannot be added. Guest list is full. \n");
        }//end if

    }//end method

    //*************************************
    //Method to print party
    public void printParty()
    {
        System.out.println("****************************************************\n");
        System.out.println("Guest list for " +
        this.host + "'s party is: \n\n" +
        this.guests + ".\n");

    } // end Print Party method

    }//end class party

Answer 1

创建第二个名为 rejectedGuests 的 ArrayList，每当客人被拒绝时，将他们添加到该列表中。然后放一个 getter 方法来检索列表。从那里它只是一个简单的 String.format() 调用和一个 println() 语句。

Answer 2

添加 extraGuest 字段：

private ArrayList<String> extraGuest;

在 addGuest(guest) 方法的 else 块中添加 extraGuest。

import java.util.ArrayList;

public class Party2
{
 // instance variables that will hold your data
 // private indicates they belong to this class exclusively
 private int maxGuests;
 private String host;
 private ArrayList<String> guests;
 private ArrayList<String> extraGuest;

 //Constructor
 public Party2(int maxGuests, String host)
 {
    System.out.println("Maximum number of guests: " + maxGuests + ".  Guest list for " + host + "'s party. \n");
    this.guests = new ArrayList<String>();
    this.extraGuest = new ArrayList<String>();
    this.maxGuests = maxGuests;
    this.host = host;
 }

 //getter
 // define type of data to be returned
 public String getHost()
 {
    System.out.println("Setting host to: " + host);
    return host;
 }

 //setter
 // setters have type void b/c they return nothing
 public void setHost(String host)
 {
    System.out.println("Setting host to: " + host);
    this.host = host;
 }

 //*************************************
 //Method to add to guest list
 public void addGuest(String guest)
 {

    if (guests.size() < maxGuests)
    {
        System.out.println("Guest: " + guest + "\n");
        this.guests.add(guest);
    }

    else
    {
        extraGuest.add(guest);
        System.out.println("     Guest cannot be added. Guest list is full. \n");
    }//end if

 }//end method

 //*************************************
 //Method to print party
 public void printParty()
 {
      System.out.println("****************************************************\n");
    System.out.println("Guest list for " +
    this.host + "'s party is: \n\n" +
    this.guests + ".\n");

    System.out.println(extraGuest+"weren't added to the list because the guest list is full");

 } // end Print Party method

}//end class party

访问 ArrayList 中的特定元素

Accessing specific elements in an ArrayList

java

class

methods

arraylist

indexoutofboundsexception