我有一个 FlowerClass 对象的 ArrayList。每个 FlowerClass 对象都有一个名称。我想遍历 ArrayList 并对它们进行计数。我想显示每个的金额。因此，如果我有三个名为 Rose 的 FlowerClass 对象、两个名为 Daffodil 的对象和一个名为 Tulip 的对象...我想显示以下内容:
- 找到 3 朵玫瑰
- 找到 3 朵水仙花
- 找到 3 朵郁金香
到目前为止，我已经使用我制作的两个函数正确计数了。问题是我迭代整个 ArrayList...所以它会多次向我显示结果。例如，如果用户添加 3 朵玫瑰和 2 朵水仙花...输出如下:
- 找到 3 朵玫瑰
- 找到 3 朵玫瑰
- 找到 3 朵玫瑰
- 找到 2 朵水仙花
- 找到 2 朵水仙花
我知道代码为什么这样做，但我不知道如何删除重复的输出。我也不知道如何正确实现集合。我之前在字符串的 ArrayList 上使用过 Collections...并且它有效。但这次我将在对象的 ArrayList 上使用集合，并且我想检查每个特定名称的频率。这是主类:
import java.util.Scanner;
import java.util.ArrayList;
import java.util.Collections;
public class MainClass {
static ArrayList<FlowerClass> flowerPack = new ArrayList<FlowerClass>();
public static void main(String[] args){
Scanner input = new Scanner(System.in);
while(true){
System.out.println("1. Add flower to flowerpack.");
System.out.println("2. Remove flower from the flowerpack.");
System.out.println("3. Search for a flower in the flowerpack.");
System.out.println("4. Display the flowers in the flowerpack.");
System.out.println("5. Exit the program.");
int userChoice = input.nextInt();
switch(userChoice){
case 1:
addFlower();
break;
case 2:
searchFlower();
break;
case 3:
displayFlowers();
break;
case 4:
System.out.println("Goodbye!");
System.exit(0);
}
}
}
public static void addFlower(){
if (FlowerClass.numberFlowers() == 25){
System.out.println("There are 25 flowers in the flowerpack. Remove at least one in order to add more.");
return;
}
Scanner input = new Scanner(System.in);
System.out.println("What is the flower's name?");
String desiredName = input.nextLine();
System.out.println("What is the flower's color?");
String desiredColor = input.nextLine();
System.out.println("How many thorns does it have?");
Scanner input2 = new Scanner(System.in);
int desiredThorns = input2.nextInt();
System.out.println("What does it smell like?");
String desiredSmell = input.nextLine();
flowerPack.add(new FlowerClass(desiredName, desiredColor, desiredThorns, desiredSmell));
}
public static void searchFlower(){
System.out.println("Enter the flower you want to search for.");
Scanner input = new Scanner(System.in);
String userChoice = input.nextLine();
int occurrences = 0;
for (FlowerClass flower: flowerPack){
String name = flower.getName();
if (userChoice.equals(name)){
occurrences++;
}
else if(occurrences == 0){
System.out.println("Match not found.");
return;
}
}
System.out.println("Found " + occurrences + " " + userChoice);
}
public static void searchFlower(String desiredFlower){
int occurrences = 0;
String userChoice = desiredFlower;
for (FlowerClass flower: flowerPack){
String name = flower.getName();
if (userChoice.equals(name)){
occurrences++;
}
}
System.out.println("Found " + occurrences + " " + userChoice);
}
public static void displayFlowers(){
int repeats = 0;
/*for (FlowerClass flower: flowerPack){
System.out.println(flower.getName());
}
System.out.println("Number of flowers in pack: " + FlowerClass.numberFlowers());*/
//int occurrences = Collections.frequency(flowerPack, name);
//System.out.println(name + ": " + occurrences);
for (FlowerClass flower: flowerPack){
String name = flower.getName();
searchFlower(name);
}
}
}
这是 FlowerClass:
public class FlowerClass {
public static int numberOfFlowers = 0;
public String flowerName = null;
public String flowerColor = null;
public int numberThorns = 0;
public String flowerSmell = null;
FlowerClass(){
}
FlowerClass(String desiredName, String desiredColor, int desiredThorns, String desiredSmell){
flowerName = desiredName;
flowerColor = desiredColor;
numberThorns = desiredThorns;
flowerSmell = desiredSmell;
numberOfFlowers++;
}
public void setName(String desiredName){
flowerName = desiredName;
}
public String getName(){
return flowerName;
}
public static int numberFlowers(){
return numberOfFlowers;
}
}
如果您查看主类中的最后一个函数，您会发现我注释掉了我尝试实现 Collections.Frequency 的方式。我还尝试制作一个多维字符串数组，并在数组中存储花的名称和花的数量。这正确地计算了所有内容，但我不确定如何在计数旁边显示名称。它变得非常困惑，所以我暂时放弃了这种尝试，转而尝试其他两种选择。如果我能找到一种方法来删除重复的输出行(或者如果我能找到一种让集合工作的方法)，那么我就不需要修改多维数组。
任何提示将不胜感激。感谢您的时间。
最佳答案
有趣的代码，但它并不像我想要的那样工作。
在当前的情况下，正如您所做的那样，您需要跟踪已经遇到的花名称:
public static void displayFlowers(){
//int repeats = 0;
List<String> displayedFlowerTypes = new ArrayList<String>();
for (FlowerClass flower: flowerPack){
String name = flower.getName();
if(!displayedFlowerTypes.contains(name))
{
displayedFlowerTypes.add(name);
searchFlower(name);
}
}
}
我宁愿做的是维护一个 map 来跟踪花类型的计数，并从中获取类型的数字:
public class MainClass {
static List<FlowerClass> flowerPack = new ArrayList<FlowerClass>();
static Map<String, Integer> flowerCount = new HashMap<String, Integer>();
public static void addFlower() {
if (FlowerClass.numberFlowers() == 25) {
System.out.println("There are 25 flowers in the flowerpack. Remove at least one in order to add more.");
return;
}
Scanner input = new Scanner(System.in);
System.out.println("What is the flower's name?");
String desiredName = input.nextLine();
System.out.println("What is the flower's color?");
String desiredColor = input.nextLine();
System.out.println("How many thorns does it have?");
Scanner input2 = new Scanner(System.in);
int desiredThorns = input2.nextInt();
System.out.println("What does it smell like?");
String desiredSmell = input.nextLine();
flowerPack.add(new FlowerClass(desiredName, desiredColor, desiredThorns, desiredSmell));
if(!flowerCount.containsKey(desiredName))
{
flowerCount.put(desiredName, 1);
}
else
{
int currentCount = flowerCount.get(desiredName);
flowerCount.put(desiredName, currentCount+1));
}
}
这样，您就可以按如下方式显示花朵:
public static void displayFlowers() {
for (String name : flowerCount.keySet()) {
//searchFlower(name);
System.out.println("Found " + flowerCount.get(name) + " " + name);
}
}
关于java - 使用 Collections 或我的函数计算 ArrayList 中对象的出现次数，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/24337786/