Objects and Collections - General Questions

What is the output of the following program?

public class Main {
    public static void main(String[] args) {
        java.util.Queue<Integer> q = new java.util.LinkedList<>();
        q.offer(1); q.offer(2); q.offer(3);
        System.out.println(q.poll() + " " + q.size());
    }
}

What is the output of the following program?

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Map<Character, Integer> freq = new TreeMap<>();
        for (char c : "banana".toCharArray()) freq.merge(c, 1, Integer::sum);
        System.out.println(freq);
    }
}

What is the output of the following program?

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Set<String> s = new HashSet<>();
        s.add("a"); s.add("b"); s.add("a");
        System.out.println(s.size());
    }
}

Which Map implementation keeps insertion order?

What is the output of the following program?

public class Main {
    public static void main(String[] args) {
        java.util.List<Integer> l = new java.util.ArrayList<>(java.util.List.of(10, 20, 30));
        l.remove(Integer.valueOf(10));
        l.remove(0);
        System.out.println(l);
    }
}