Interview questions - Level 4

From ChatGPT I havent verfied it so feel free to comment if there is a mistake. 1. What do anonymous inner classes become after being compiled? After being compiled, anonymous inner classes become separate class files named using the enclosing class name followed by a $ and a number, e.g., OuterClass$1.class. 2. Can inner classes be inherited? Yes, inner classes can be inherited, but only if they are not private. 3. Can anonymous inner classes be inherited? No, anonymous inner classes cannot be inherited because they do not have a name to refer to. 4. Can you override inner classes? No, you cannot override inner classes, but you can shadow them by declaring another class with the same name in a subclass. 5. What limitations do local classes have? Local classes cannot have static declarations and can only access final or effectively final variables from their enclosing method or block. 6. Can an anonymous inner class contain static methods? No, an anonymous inner class cannot contain static methods because it is implicitly tied to an instance of its enclosing class. 7. Can you create an instance of an inner class if the outer class only has a private constructor? Yes, you can create an instance of an inner class if the outer class only has a private constructor, but it must be done from within the outer class or through a method provided by the outer class. 8. Can you declare inner classes as private? Yes, you can declare inner classes as private. 9. Can you declare anonymous inner classes as private? No, you cannot explicitly declare an anonymous inner class as private because its scope is already limited to the enclosing block or expression. 10. How many inner classes can a class have? A class can have any number of inner classes; there is no predefined limit.

Hi! Can someone me help with 10th question? How many inner classes can a class have?

6. In Java 8: no, in newer versions (from 16 on): yes https://www.oracle.com/java/technologies/javase/16-relnote-issues.html#JDK-8246771

I'm confused with the 4th question - if I inherit inner class, think there's no problem to override any non-final method of this inner class. But what is meant by "overriding inner class"?

public class Polymorphism {

    public static class A {
        public class InnerA {
            public void print() {
                System.out.println("A.InnerA");
            }
        }

        public int someVar = 1;
    }

    public static class B extends A {
        public class InnerA {
            public void print() {
                System.out.println("B.InnerA");
            }
        }

        public int someVar = 321; // variable shadowing

    }

    public static void main(String[] args) {
        A b1 = new B();
        B b2 = new B();

        // fields: no polymorphism, shadowing
        System.out.println(b1.someVar);
        System.out.println(b1.someVar);

        // no polymorphism but also no shadowing
        b1.new InnerA().print();
        b2.new InnerA().print();
        
        // for methods this should be clear. If it's overridden methods then b1.method() and b2.method() always would
        // invoke the overridden version.
    }
}

Can someone help me with these please? I haven't found anything on the internet. 7. Can you create an instance of an inner class if the outer class only has a private constructor? 9. Can you declare anonymous inner classes as private?

public class Solution {
    public static class Test {
        private Test() {
        }
        public void testMethod() {
        }
    }
    public static void main(String[] args) {
        new Test();
    }
}

public class Solution {
    private Solution() {

    }

    public static class Test {
        public void testMethod() {
        }
    }

    public class TestNonStatic {
        public void testMethod2() {
        }
    }
    public static void main(String[] args) {
        new Test();
        new Solution().new TestNonStatic();
    }
}