为什么 getter 方法不 return 任何对象的属性？

Question

我的程序应该return 两个不同对象的不同属性。在我的主要方法中，我在创建新对象时将这些属性设置为参数。但是当我调用那些 getter 方法时（我已经在单独的 class 中编写了这些方法，如果需要，我可以 post 那 class），它不会 return 所有属性.它只打印出第一个属性（也被设置为第一个参数），而不是其他两个值。不知道哪里做错了

我的代码：主要class：

    package main;

public class Main {

    public static void main(String[] args) {

        //creating object for book 1 
        Book book1 = new Book("The brief history of time", "111", new String[]{"S. hawking", "hawking's friends"});
        //creating object for book 2
        Book book2 = new Book("100 years of solitude", "222", new String[]{"G.marquez", "marquez's friend"});

        System.out.println("All info for the first book: \n");

        System.out.println("Name: " + book1.getName());
        System.out.println("ISBN: " + book1.getIsbn());
        System.out.println("Authors: " + book1.getAuthors());

        System.out.println("\n\n");
        System.out.println("All info for the second book: \n");
        System.out.println("Name: " + book2.getName());
        System.out.println("ISBN: " + book2.getIsbn());
        System.out.println("Authors: " + book2.getAuthors());

    }

}

图书class:

    package main;

public class Book {
    //variables

    private String name;
    private String isbn;
    private String[] authors;

    //constructors
    public Book(String name, String isbn, String[] authors) {
        this.name = name;
        this.isbn = name;
        this.authors = authors;

    }

    //setters
    public void setName(String name) {
        this.name = name;
    }

    public void setIsbn(String isbn) {
        this.isbn = isbn;
    }

    public void setAuthors(String[] authors) {
        this.authors = authors;
    }

    //getters
    public String getName() {
        return name;
    }

    public String getIsbn() {
        return isbn;
    }

    public String[] getAuthors() {
        return authors;
    }

}

Answer 1

您需要迭代 authors 数组才能打印其中的字符串。像这样：

    System.out.println("All info for the first book: \n");

    System.out.println("Name: " + book1.getName());
    System.out.println("ISBN: " + book1.getIsbn());
    for (String author : book1.getAuthors()) {
        System.out.println("Author: " + author);
    }

你的 Book class 构造函数也有问题：

public Book(String name, String isbn, String[] authors) {
    this.name = name;
    this.isbn = name; // this.isbn is not name!
    this.authors = authors;
}

必须是：

public Book(String name, String isbn, String[] authors) {
    this.name = name;
    this.isbn = isbn;
    this.authors = authors;
}

Answer 2

当你想打印一个字符串数组时，你可以使用这个。

System.out.println(Arrays.toString(book1.getAuthors()));

Answer 3

Book 构造函数有问题：

public Book(String name, String isbn, String[] authors) {
    this.name = name;
    this.isbn = name; // you are setting isbn as name! 
    this.authors = authors;   
}

我认为您需要定义 getAuthors 打印作者数组的方式，例如 What's the simplest way to print a Java array?

为什么 getter 方法不 return 任何对象的属性？

Why getter method doesn't return any object's attribute?

java

arrays

object

return-value

getter-setter