从内部类对象获取外部类对象

public class OuterClass {
    private String message = "Hello from OuterClass!";

    public class InnerClass {
        public void displayMessage() {
            System.out.println(message);
        }
    }
}

OuterClass outer = new OuterClass();
OuterClass.InnerClass inner = outer.new InnerClass();
inner.displayMessage();