如何访问本地内部类中的外部类方法局部变量？

Question

public class MyClass {
    int x=9;
    public static void main(String args[]) {
       MyClass  myClass = new MyClass();
       myClass.test();
    }

    public void test(){
        int x=10;

        class InnerClass{
            int x = 11;

            void print(){
               int x = 12;
               System.out.println(x); 
               System.out.println(this.x); 
               System.out.println(MyClass.this.x); 
               System.out.println("MyClass => test() => x :" + "?");
            }
        }
        InnerClass innerClass = new InnerClass();
        innerClass.print();
    }
}

How to call MyClass test() method local variable x inside the InnerClass print() method. What i can write in place of ? in last System.out.println() method in order to get the value of test() x .

Answer 1

Unfortunately in Java you can't.

The only way to access the x in MyClass::test would be to rename both variables in your inner class and in your inner class method into something else.

There is no need though to rename the outer class field x as InnerClass::print would consider the variable in the most-inner scope.

Although this snippet is for demonstration purposes, better practice would have you have different and more significant names for each variable.

Answer 2

That works fine for me:

public class Outerclass {

    public static void main(String args[]) {
        Outerclass outer = new Outerclass();
        outer.outerMethod();
    }

    // method of the outer class 
    void outerMethod() {
        int num = 23;

        // method-local inner class
        class MethodInnerClass {
            public void print() {
                System.out.println("This is method inner class "+num);
            }
        }
        // Accessing the inner class
        MethodInnerClass inner = new MethodInnerClass();
        inner.print();
    }
}

Answer 3

打印外部类变量使用

 MyClass.this.x