我正在创建一个 Java 程序，允许用户输入一组相关项目，然后将它们按照从大到小的顺序排列。代码的第一部分允许用户输入任意数量的项目，除非他们键入“STOP”，否则用户的输入将存储在 ArrayList 中。例如：
`请输入您想要添加到排名列表中的项目，或输入“停止”结束程序。
星球大战
请输入您想要添加到排名列表中的项目，或输入“停止”以结束该计划。
哈利·波特
请输入您想要添加到排名列表中的项目，或输入“停止”以结束该计划。
指环王
请输入您想要添加到排名列表中的项目，或输入“停止”以结束该计划。
停止`
预期结果应该是：
You have entered: Star Wars Harry Potter The Lord of the Rings程序的这一部分已经完成，但我真的很难弄清楚下一步 - 实际排名。因为 ArrayList 中可以输入的内容没有限制，所以我不确定如何指示程序对输入的项目进行排名。我知道我想提示用户在输入的不同项目之间进行选择（“您更喜欢项目 A 还是项目 B？”），但我不确定当 ArrayList 没有可以输入的内容有限制。我可以得到一些指导吗？
`//Ranking.java是一个旨在提示用户相关项目列表的程序 //并将它们存储在数组中。然后程序会提示用户排名 //这些项目从最大到最小然后打印出它们的排名
//import Scanner and ArrayList
import java.util.*;
//declare class
public class Ranking {
//declare main method
public static void main(String[] args) {
//initialize scanner
Scanner input = new Scanner(System.in);
//create ArrayList to store items
ArrayList<String> items = new ArrayList<String>();
//introduction
System.out.println("Welcome to Ranking.java!");
//while loop that repeats the prompt unless the user enters "STOP"
while(true) {
//prompt
System.out.print("\nPlease enter an item you wish to add to the ranking list, "
+ "or type 'STOP' to end the program.\n>> ");
//stored in item variable
String item = input.nextLine();
//if item equals "STOP," program breaks and prints out the list of items entered
if(item.equals("STOP")) {
System.out.println("\nYou have entered:");
for(int i = 0; i < items.size(); i++) {
System.out.println(items.get(i));
}
break;
}
//otherwise it adds to the ArrayList
else {
items.add(item);
}
}
ArrayList<String> itemsRanked = new ArrayList<String>();
//ranking introduction
System.out.println("\nYou may now rank the following from greatest to least.\n");
}
}
我修改了你的代码并添加了一些代码。这是我的测试结果之一。
Welcome to Ranking.java!
Please enter an item you wish to add to the ranking list, or type 'STOP' to end the program.
>> Item 1
Please enter an item you wish to add to the ranking list, or type 'STOP' to end the program.
>> Item 2
Please enter an item you wish to add to the ranking list, or type 'STOP' to end the program.
>> Item 3
Please enter an item you wish to add to the ranking list, or type 'STOP' to end the program.
>> stop
For item Item 1, enter a ranking from 1 to 3
>> 3
For item Item 2, enter a ranking from 1 to 3
>> 2
For item Item 3, enter a ranking from 1 to 3
>> 1
You ranked Item 3 as 1
You ranked Item 2 as 2
You ranked Item 1 as 3
我做的第一件事是创建一个
RankItemintStringpublic class RankItem {
private int rank;
private final String item;
public RankItem(String item) {
this.item = item;
}
public int getRank() {
return rank;
}
public void setRank(int rank) {
this.rank = rank;
}
public String getItem() {
return item;
}
}
接下来，我将你的代码分为四种方法。第一个方法读取项目，第二个方法读取排名，第三个方法将
ListList分而治之。
如果用户输入多个相似的排名，则排序会按排名、字母顺序对列表进行排序。排名值可以是任何正值
int这是完整的可运行代码。我将附加类设置为内部类，这样我就可以将代码作为一个块发布。
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Scanner;
// Ranking.java is a program designed to prompt user for a list of related items
// and stores them in an array. The program will then prompt the users to rank
// those items from greatest to least then prints out their ranking.
public class RankingItems {
public static void main(String[] args) {
RankingItems ri = new RankingItems();
ri.processItems();
}
private final List<RankItem> rankItems;
private final Scanner input;
public RankingItems() {
this.rankItems = new ArrayList<>();
this.input = new Scanner(System.in);
}
public void processItems() {
readItems();
rankItems();
sortItems();
writeItems();
}
private void readItems() {
System.out.println("Welcome to Ranking.java!");
System.out.println();
while (true) {
// prompt
System.out.println("Please enter an item you wish to "
+ "add to the ranking list, "
+ "or type 'STOP' to end the program.");
System.out.print(">> ");
String item = input.nextLine();
if (item.equalsIgnoreCase("STOP")) {
return;
} else {
rankItems.add(new RankItem(item));
}
}
}
private void rankItems() {
System.out.println();
for (RankItem rankItem : rankItems) {
int rank = -1;
while (rank < 0) {
System.out.println("For item " + rankItem.getItem()
+ ", enter a ranking from 1 to " + rankItems.size());
System.out.print(">> ");
String rankString = input.nextLine();
try {
rank = Integer.valueOf(rankString);
rankItem.setRank(rank);
} catch (NumberFormatException e) {
continue;
}
}
}
}
private void sortItems() {
Collections.sort(rankItems, new Comparator<RankItem>() {
@Override
public int compare(RankItem o1, RankItem o2) {
if (o1.getRank() > o2.getRank()) {
return 1;
} else if (o1.getRank() < o2.getRank()) {
return -1;
} else {
return o1.getItem().compareTo(o2.getItem());
}
}
});
}
private void writeItems() {
System.out.println();
for (RankItem rankItem : rankItems) {
System.out.println("You ranked " + rankItem.getItem() + " as "
+ rankItem.getRank());
}
}
public class RankItem {
private int rank;
private final String item;
public RankItem(String item) {
this.item = item;
}
public int getRank() {
return rank;
}
public void setRank(int rank) {
this.rank = rank;
}
public String getItem() {
return item;
}
}
}