java - 为什么这个 java 代码没有在 Eclipse IDE 上显示。公共(public)类型App必须在自己的文件中定义

Question

这个问题已经有答案了:

Java compiler error: "public type .. must be defined in its own file"? (5 个回答)

已关闭 4 年前。

为什么这段java代码没有运行？我正在尝试创建类，然后从类中创建对象。代码没有编译通过，它说**公共(public)类型应用程序必须在其自己的文件中定义**请帮忙。

public class Book{
    public String title;
    public String author;
    public int numPages;
}

public class App
{
    public static void main(String [] args)
    {
          Book book1 = new Book();
          book1.title = "Harry Potter";
          book1.author = "JK Rowling";
          book1.numPages = 400;

          System.out.println(book1.title);

          Book book2 = new Book();
          book2.title = "Lord of the Rings";
          book2.author = "JRR Tolkien";
          book2.numPages = 300;

          System.out.println(book2.title);
    }
}

Answer 1

• 公共(public)类型 Book 必须在其自己的文件中定义 - java 那里对于每个公共(public)类型，应该是项目中的单独文件。所以你应该再做一个

• 要么应该将类声明为静态类，要么应该是一个单独的文件

• 我已经包含了您在其中添加的 Book.classApp.class为静态，会对你有帮助

//The public type Book must be defined in its own file 

//public class Book{
//    public String title;
//    public String author;
//    public int numPages;
//}   

public class App
{
    public static void main(String [] args)
    {
          Book book1 = new Book();
          book1.title = "Harry Potter";
          book1.author = "JK Rowling";
          book1.numPages = 400;

          System.out.println(book1.title);

          Book book2 = new Book();
          book2.title = "Lord of the Rings";
          book2.author = "JRR Tolkien";
          book2.numPages = 300;

          System.out.println(book2.title);
    }
    public static class Book{
        public String title;
        public String author;
        public int numPages;
    }

}

结果: