我不认为我会因为使用常规数组的强力方法完成此操作而遇到麻烦。我正在尝试使用Collections.frequency将来自用户的重复条目组合在一起,并显示每个条目发生的次数(如果不止一次);但是,输出只是在输入时打印。我有两个课程,我将在下面展示:
public class Flower {
private String name;
private String color;
private String smell;
private String hasThorns;
public Flower(String name, String color, String smell, String hasThorns) {
this.name = name;
this.color = color;
this.smell = smell;
this.hasThorns = hasThorns;
}
public void setName(String name) {
this.name = name;
}
public void setColor(String color) {
this.color = color;
}
public void setSmell(String smell) {
this.smell = smell;
}
public void setThorns(String hasThorns) {
this.hasThorns = hasThorns;
}
public String getName() {
return name;
}
public String getColor() {
return color;
}
public String getSmell() {
return smell;
}
public String getThorns() {
return hasThorns;
}
public String toString() {
return "Name: " + this.name + ", Color: " + this.color + ", Scent? " + this.smell + ", Thorns? " + this.hasThorns;
}
}//end Flower class
import java.util.*;
public class Assignment3 {
String name = new String();
String color = new String();
String smell = new String();
String hasThorns = new String();
//ArrayList<Flower> flowerPack = new ArrayList<Flower>();
boolean found = false;
public static void main(String[] args) {
new Assignment3();
}
// This will act as our program switchboard
public Assignment3() {
Scanner input = new Scanner(System.in);
ArrayList<Flower> flowerPack = new ArrayList<Flower>();
System.out.println("Welcome to my flower pack interface.");
System.out.println("Please select a number from the options below");
System.out.println("");
while (true) {
// Give the user a list of their options
System.out.println("1: Add an item to the pack.");
System.out.println("2: Remove an item from the pack.");
System.out.println("3: Search for a flower.");
System.out.println("4: Display the flowers in the pack.");
System.out.println("5: Filter flower pack by incomplete name");
System.out.println("0: Exit the flower pack interface.");
// Get the user input
int userChoice = input.nextInt();
switch (userChoice) {
case 1:
addFlower(flowerPack);
break;
case 2:
removeFlower(flowerPack);
break;
case 3:
searchFlowers(flowerPack);
break;
case 4:
displayFlowers(flowerPack);
break;
case 5:
filterFlowers(flowerPack);
break;
case 0:
exitInterface();
break;
default:
System.out.println("Invalid entry. \nPlease choose between 1-5, or 0: ");
break;
}
}
}
private void addFlower(ArrayList<Flower> flowerPack) {
// TODO: Add a flower that is specified by the user
Flower newFlower = new Flower(name, color, smell, hasThorns);
Scanner input = new Scanner(System.in);
if(flowerPack.size() < 25)
{
System.out.println("Enter the name of the flower you wish to add: ");
newFlower.setName(input.nextLine());
System.out.println("Enter the color of the flower: ");
newFlower.setColor(input.nextLine());
System.out.println("Does the flower have a scent? Yes or No: ");
newFlower.setSmell(input.nextLine());
System.out.println("Does the flower have thorns? Yes or No: ");
newFlower.setThorns(input.nextLine());
flowerPack.add(newFlower);
}
else
{
System.out.println("You may only hold 25 flowers in your flower pack. Please remove at least one before adding another.");
}
}
private void removeFlower(ArrayList<Flower> flowerPack) {
// TODO: Remove a flower that is specified by the user
Scanner input = new Scanner(System.in);
System.out.println("Enter the name of the flower you want to remove: ");
String deleteName = input.nextLine();
System.out.println("Enter the color of the flower you want to remove: ");
String deleteColor = input.nextLine();
System.out.println("Is this a flower with a scent? Yes or No: ");
String deleteSmell = input.nextLine();
System.out.println("Is this a flower with thorns? Yes or No: ");
String deleteThorns = input.nextLine();
for(int i = 0; i < flowerPack.size(); i++) {
if(flowerPack.get(i).getName().equals(deleteName) && flowerPack.get(i).getColor().equals(deleteColor) && flowerPack.get(i).getSmell().equals(deleteSmell) && flowerPack.get(i).getThorns().equals(deleteThorns))
{
flowerPack.remove(i);
found = true;
break;
}
if(found)
{
System.out.println("That flower was successfully removed from your inventory.");
}
else
{
System.out.println("That flower was not found in your inventory.");
}
}
}
private void searchFlowers(ArrayList<Flower> flowerPack) {
// TODO: Search for a user specified flower
}
这就是我遇到问题的地方。我没有启动其他方法(搜索,过滤),因为我希望它在继续之前正确显示。
private void displayFlowers(ArrayList<Flower> flowerPack) {
// TODO: Display flowers using any technique you like
for(Flower flower : flowerPack) {
int duplicates = Collections.frequency(flowerPack, flower);
System.out.println(flower + " - " + duplicates);
}
}
private void filterFlowers (ArrayList<Flower> flowerPack) {
// TODO Filter flower results
}
private void exitInterface() {
Scanner input = new Scanner(System.in);
System.out.println("Are you sure you want to exit the flower pack interface? Y or N: ");
while(true) {
String answer = input.next();
if(!"Y".equalsIgnoreCase(answer) && !"N".equalsIgnoreCase(answer))
{
System.out.println("Please enter Y or N (not case-sensitive): ");
}
if("Y".equalsIgnoreCase(answer))
{
System.out.println("Thank you for using the flower pack interface. See ya later!");
System.exit(0);
}
if("N".equalsIgnoreCase(answer))
{
break;
}
}
}
}
我已经看过使用Maps / HashSets的示例,但我现在对这些概念不太熟悉,无法使用它们。
这是输出,这是不正确的。有人能给我一个关于我哪里出错的提示吗?
Name: rose, Color: red, Scent? yes, Thorns? yes - 1
Name: rose, Color: red, Scent? yes, Thorns? yes - 1
Name: rose, Color: pink, Scent? yes, Thorns? no - 1
Name: daffodil, Color: yellow, Scent? yes, Thorns? no - 1
正如您所看到的,前两个条目应该是一个,但是-2:
像:
Name: rose, Color: red, Scent? yes, Thorns? yes - 2
答案 0 :(得分:1)
你的花类需要一个等号和哈希码方法,否则java不能判断两个花对象是否相同。
答案 1 :(得分:0)
Collections.frequency
使用Flower.equals
来判断两朵花是否相同。由于您尚未覆盖equals
的默认实施,因此Flower
的所有实例都显示为唯一。
您可以使用IDE生成应该运行良好的equals
(和hashCode
)实现,
然后频率计数将变为正确,
因为逻辑上相同的花朵会被检测出来。
例如,由IntelliJ生成,请在Flower
:
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
Flower flower = (Flower) o;
if (color != null ? !color.equals(flower.color) : flower.color != null) {
return false;
}
if (hasThorns != null ? !hasThorns.equals(flower.hasThorns) : flower.hasThorns != null) {
return false;
}
if (name != null ? !name.equals(flower.name) : flower.name != null) {
return false;
}
if (smell != null ? !smell.equals(flower.smell) : flower.smell != null) {
return false;
}
return true;
}
@Override
public int hashCode() {
int result = name != null ? name.hashCode() : 0;
result = 31 * result + (color != null ? color.hashCode() : 0);
result = 31 * result + (smell != null ? smell.hashCode() : 0);
result = 31 * result + (hasThorns != null ? hasThorns.hashCode() : 0);
return result;
}