我正在努力学习Java，并且非常努力理解课程。我在一个类中有一个String数组，我需要将它放入一个对象的arrayList中，然后在另一个类的方法中使用arrayList的getter和setter。以下是我的一些代码：
public class Store
{
public static void main(String[] args) {
Book book1 = new Book();
Book book2 = new Book();
Book book3 = new Book();
printAll();
}
public void printAll(){
for(String book : booksOnHand){
super.print()
}
}
}
public class Book extends Store
{
private String title;
private String author;
private int year;
int[] stock = new int[4];//how many books are on hand at each of 5 stores
String [] books = {"War and Peace, Leo Tolstoy, 1869, 12, 7, 3, 9",
"Little Women, Louisa May Alcott, 1868, 4, 5, 2, 8",
"To Kill A Mockingbird, Harper Lee, 1960, 21, 18, 13, 6",
};
ArrayList<Book> booksOnHand = new ArrayList<Book>();
public Book(String title, String author, int year, int [] stock)
{
this.title = title;
this.author = author;
this.year = year;
this.stock = stock;
}
public String getTitle()
{
return title;
}
public String getAuthor()
{
return author;
}
public String getYear()
{
return year;
}
public int[] getStock()
{
return stock;
}
public void setTitle(String title)
{
this.title = title;
}
public void setAuthor(String author)
{
this.author = author;
}
public void setYear(int year)
{
this.year = year;
}
public void setStock(int count1, int count2, int count3, int count4)
{
stock[0] = count1;
stock[1] = count2;
stock[2] = count3;
stock[3] = count4;
}
void print()
{
System.out.println("Title: " + getTitle() + "\tAuthor: " + getAuthor() + "\tYear: " + getYear() + "\tStock: " + Arrays.toString(getStock()));
}
}
我有更多代码，包括Collections.addAll(booksOnHand, books);
但我不知道将arrayList放在何处以及如何实例化它，以便我可以在其他类中使用它。提前感谢所有愿意提供帮助的人！
答案 0 :(得分：1)
我做了一些更正，请尝试下面的代码。我在代码中添加了一些评论。
import java.util.ArrayList;
import java.util.List;
public class Store {
private static List<Book> booksOnHand = new ArrayList<Book>();
public static void main(String[] args) {
// you should create you object with your constructure
Book book1 = new Book("War and Peace", "Leo Tolstoy", 1869, 12, 7, 3, 9);
Book book2 = new Book("Little Women", "Louisa May Alcott", 1868, 4, 5, 2, 8);
Book book3 = new Book("To Kill A Mockingbird", "Harper Lee", 1960, 21, 18, 13, 6);
// add them into a list
booksOnHand.add(book1);
booksOnHand.add(book2);
booksOnHand.add(book3);
printAll();
}
public static void printAll() {
// print them with its own object method.
for (Book book : booksOnHand) {
book.print();
}
}
}
import java.util.Arrays;
// book shouldn't extends store, so I removed that
public class Book {
private String title;
private String author;
private int year;
int[] stock = new int[4];// how many books are on hand at each of 5 stores
// with int...(vararg) you can add stocks of stores
public Book(String title, String author, int year, int...stock) {
this.title = title;
this.author = author;
this.year = year;
this.stock = stock;
}
public String getTitle() {
return title;
}
public String getAuthor() {
return author;
}
public int getYear() {
return year;
}
public int[] getStock() {
return stock;
}
public void setTitle(String title) {
this.title = title;
}
public void setAuthor(String author) {
this.author = author;
}
public void setYear(int year) {
this.year = year;
}
// use varargs instead of "int count1, int count2, int count3, int count4"
public void setStock(int... stock) {
this.stock = stock;
}
void print() {
System.out.println("Title: " + getTitle() + "\tAuthor: " + getAuthor()
+ "\tYear: " + getYear() + "\tStock: "
+ Arrays.toString(getStock()));
}
}
打印：
标题：战争与和平作者：列夫托尔斯泰年份：1869年股票：[12,7,3,9]
标题：小女人作者：Louisa May Alcott年份：1868年股票：[4,5,2,8]
标题：杀死一只知更鸟作者：Harper Lee年份：1960年股票：[21,18,13,6]
答案 1 :(得分：1)
根据它们在现实生活中所代表的对象来考虑Java类。书不应该扩展商店。当你使用扩展时，你会说＆＃34;这个对象就像这个，但更具体。＆＃34;
所以你可能有一个名为Vehicle的类。所有车辆都有发动机。但是你可能会有不同类型的车辆做不同的事情。因此，您可能会有一个可以扩展车辆的类Car和一个可以扩展车辆的类船。它们都有发动机，但它们的动作不同。这个概念称为继承。在你的情况下，没有必要使用它。
类和对象之间也存在差异。一个类就像一个蓝图。 Class Car了解汽车需要知道的所有事情。从Car类创建对象时，可以指定颜色，速度等属性。这就是您不需要标题数组等的原因。蓝图不需要特定的值，只知道在构建书时会有一个名为title的String，它将包含标题。
在您的情况下，想一想书店是如何运作的。书店的书籍记录是否知道其他商店是否有该书。没有。
我还有一个名为main的不同类，您可以使用main方法，然后将Store视为表示存放书籍的商店的类。将您的ArrayList放在这个类中，并使用store中的方法来访问每个标题手头有多少本书的信息。
一般设置应该更像：
public class Main {
public static void main(String[] args) {
Store barnesAndNoble = new Store();
Book book1 = new Book("War and Peace", "Leo Tolstoy", 1869, 12, 7, 3, 9);
Book book2 = new Book("Little Women", "Louisa May Alcott", 1868, 4, 5, 2, 8);
Book book3 = new Book("To Kill A Mockingbird", "Harper Lee", 1960, 21, 18, 13, 6);
barnesAndNoble.add(book1);
barnesAndNoble.add(book2);
barnesAndNoble.add(book3);
barnesAndNoble.printAll();
Store amazon = new Store();
amazon.add(book1);
amazon.add(book2);
amazon.add(book3);
amazon.printAll();
}
}
public class Book {
//code pertaining to books, no stock information
}
public class Store {
private List<Book> booksOnHand;
public Store() {
booksOnHand = new ArrayList<Book>();
}
public void add(Book book) {
booksOnHand.add(book);
}
//other methods for accessing the list of books, returning inventory numbers from list, or other code pertaining to listing store information
public void printAll(){
//print each books desired information
}
}