Question

我的程序应该返回两个不同对象的不同属性。在我的main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（我在一个单独的类中编写，我可以在需要时发布该类）时，它不会返回所有属性。它只打印出第一个属性（也设置为第一个参数），而不是其他两个值。我不知道我做错了什么。

我的代码：主要类：

    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());

    }

}

图书课程：

    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数组才能在其中打印字符串。像这样的东西：

    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);
    }

您的Book类构造函数中也存在问题：

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

如果要打印字符串数组，可以使用它。

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

Answer 3

Book构造函数存在问题：

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如何打印authors数组，例如What's the simplest way to print a Java array?

为什么getter方法不返回任何对象的属性？

3 个答案: