The abstract method getsql in type Data can only be defined by an abstract class报错怎么改

如果您在一个普通类中定义了一个抽象方法，并且遇到了 "The abstract method xxx in type xxx can only be defined by an abstract class" 报错，这是因为只有抽象类才能包含抽象方法，普通类不能包含抽象方法。

为了解决这个问题，您需要将这个普通类修改为抽象类。在 Java 中，您可以通过在类声明前面加上 `abstract` 关键字来将一个类定义为抽象类。同时，您还需要将抽象方法的实现留给子类去完成。例如：

public abstract class Data {
    public abstract void getSql();
    // 其他方法和属性
}

这样就成功定义了一个抽象类，并且包含了一个抽象方法 `getSql()`，它的实现将由子类去完成。注意，由于抽象类中可以包含非抽象方法和属性，因此您可以在抽象类中定义其他的方法和属性。

相关问题

The public type Student must be defined in its own fileJava(16777541) No quick fixes available

As an AI language model, I cannot perform actions on your local machine or environment. However, I can suggest a solution to the error you're getting.

The error "The public type Student must be defined in its own file" usually occurs when you have a public class defined in a file with a different name. To fix this error, you need to ensure that the public class is defined in a file with the same name as the class.

For example, if you have a public class named "Student", the file name should be "Student.java". If the class is defined in a file with a different name, you will get the error mentioned above.

Here is an example of how to define the Student class in its own file:

// Student.java file
public class Student {
    // class definition
}

Ensure that the file name and the class name are the same. If you have multiple classes defined in the same file, ensure that only one of them is public and has the same name as the file.

Once you have made the necessary changes, save the file and recompile your code. This should fix the error.

The public type ReadFileExample must be defined in its own file

这是一个错误提示，意思是在定义名为 ReadFileExample 的公共类型时，该类型必须在自己的文件中进行定义。也就是说，不能将该类型的定义放在其他文件中。这是因为公共类型需要在其它文件中使用，如果该类型的定义不在其自己的文件中，则其它文件无法访问该类型的定义。要解决这个问题，你需要将名为 ReadFileExample 的公共类型定义移到一个独立的文件中，并确保该文件被正确引用。