Local variable count defined in an enclosing scope must be final or effectively final

这是一个Java语言中的错误提示，它意味着在一个闭合的范围内定义的局部变量必须是final或有效final的，否则无法在该范围外访问。这是因为Java语言中的闭包现象，在一个内部类中使用外部类的局部变量时，要求该变量必须是final或有效final的，以便保证内部类中访问到的是外部类变量的一个副本，而不是外部类变量的一个引用，从而避免了并发访问等问题。

相关问题

Local variable row defined in an enclosing scope must be final or effectively final

The error message "Local variable row defined in an enclosing scope must be final or effectively final" is related to the concept of closures in Java. In Java, when you define a local variable inside an enclosing scope (such as a method or a loop), and you want to use that variable inside an anonymous inner class or lambda expression, the variable needs to be either final or effectively final.

A variable is effectively final if its value is not changed after initialization. If you try to modify the value of a non-final or non-effectively final variable inside an inner class or lambda expression, you will encounter this error.

To resolve this issue, you can either make the variable "row" final or effectively final by not modifying its value after initialization, or you can use a different approach, such as using a different variable or passing the value of "row" to the inner class or lambda expression explicitly.

Here's an example of making the variable final:

final int row = 10;
Runnable runnable = new Runnable() {
    @Override
    public void run() {
        System.out.println("Row: " + row);
    }
};

And here's an example of effectively final variable:

int row = 10;
Runnable runnable = () -> {
    System.out.println("Row: " + row);
};

Remember, if you modify the value of the "row" variable after its initialization, you will encounter the mentioned error.

Local variable answer defined in an enclosing scope must be final or effectively final

这是一个编译时错误，意思是在一个封闭的作用域内定义的局部变量必须是 final 或 effectively final（即在定义后不能再被修改），否则会导致编译错误。这个规则的目的是为了确保代码的可读性和可维护性，因为 final 或 effectively final 的变量在代码执行过程中不会发生变化，更容易让人理解和维护。如果你需要在封闭的作用域内修改变量，则应该使用其他方式，例如将变量定义为属性或使用 lambda 表达式等。