私はかなり新しく、Java使用してBlueJいます。プログラムを機能させるには、次のことを行う必要があります。
// Insert code here to perform a sequence of
// interactive transactions with the user.
// The user enters an item number and the program
// either displays the item or prints an error message
// if the item is not found. The program terminates
// when the user enters zero as the item number.
残念ながら、プログラムを動作させることができないようです。うまくいけば、誰かが私を助けてくれます。
これはclass Program2ループを必要とするものです:
import java.util.*;
public class Program2 {
public static void main(String[] args) {
Scanner kbd = new Scanner(System.in);
Catalog store = new Catalog(3);
int itemnum = 0;
Item item;
try {
store.insert
(new Music(1111, "Gold", 12.00, "Abba"));
store.insert
(new Movie(2222, "Mamma Mia", 16.00, "Meryl Streep"));
store.insert
(new Book(3333, "DaVinci Code", 8.00, "Dan Brown"));
store.insert
(new Music(4444, "Legend", 15.00, "Bob Marley"));
} catch (CatalogFull exc) {
System.out.println(exc);
}
// Insert code here to perform a sequence of
// interactive transactions with the user.
// The user enters an item number and the program
// either displays the item or prints an error message
// if the item is not found. The program terminates
// when the user enters zero as the item number.
itemnum = kbd.nextInt();
while (itemnum == 0) {
item = store.find(itemnum);
if (item != null) {
System.out.print(itemnum);
} else {
System.out.printf("%s was not found.%n", item);
}
System.out.println();
System.out.print("Player (0 to exit)? ");
itemnum = kbd.nextInt();
}
}
}
現時点では、現在のエラーは "(itemnum)" のループにあり、次のように言っています。
unreported exception ItemNotFound; must be caught or declared to be thrown
そうは言っても、それが唯一の問題ではなく、プログラムのこの部分を正しく実行していないと思います。うまくいけば、誰かが私を助けてくれます。前もって感謝します。
役に立つかもしれないし、役に立たないかもしれない他のいくつかのクラスを次に示します。
これはclass ItemNotFound次のとおりです。
// This exception is thrown when searching for an item
// that is not in the catalog.
public class ItemNotFound extends Exception {
public ItemNotFound(int id) {
super(String.format("Item %d was not found.", id));
}
}
これはclass CatalogFull
// This exception is thrown when trying to insert an item
// when the catalog is full.
public class CatalogFull extends Exception {
public CatalogFull() {
super("The catalog is full.");
}
}
これはclass Catalog次のとおりです。
public class Catalog {
private Item[] list;
private int size;
// Construct an empty catalog with the specified capacity.
public Catalog(int max) {
list = new Item[max];
size = 0;
}
// Insert a new item into the catalog.
// Throw a CatalogFull exception if the catalog is full.
public void insert(Item obj) throws CatalogFull {
if (list.length == size) {
throw new CatalogFull();
}
list[size] = obj;
++size;
}
// Search the catalog for the item whose item number
// is the parameter id. Return the matching object
// if the search succeeds. Throw an ItemNotFound
// exception if the search fails.
public Item find(int id) throws ItemNotFound {
for (int pos = 0; pos < size; ++pos){
if (id == list[pos].getItemNumber()){
return list[pos];
}
}
throw new ItemNotFound(id);
}
}
これはclass Item次のとおりです。
public class Item {
private int itemnum;
private String title;
private double price;
// Construct a new item object.
public Item(int id, String t, double p) {
itemnum = id;
title = t;
price = p;
}
// Return the item number of this item.
public int getItemNumber() {
return itemnum;
}
// Return the item type. This is overridden in subclasses.
public String getItemType() {
return "Item";
}
// Return a printable String represenation of this item.
public String toString() {
String line1, line2, line3, line4, out;
String itemtype = this.getItemType();
line1 = String.format("Item number: %d%n", itemnum);
line2 = String.format("Item type: %s%n", itemtype);
line3 = String.format("Item title: %s%n", title);
line4 = String.format("Item price: %.2f%n", price);
out = line1 + line2 + line3 + line4;
return out;
}
}