import java.util.HashMap;
import java.util.Map;

public class Task121125 {
    public static void main(String[] args) {
        Map<Key121125, String> map = new HashMap<>();
        
        Key121125 k1 = new Key121125(1);
        Key121125 k2 = new Key121125(1);
        
        map.put(k1, "value");
        
        System.out.println(map.containsKey(k1));
        System.out.println(map.containsKey(k2));
        
        k1.id = 2;
        
        System.out.println(map.containsKey(k1));
        System.out.println(map.containsKey(k2));
    }
    
    static class Key121125 {
        int id;
        Key121125(int id) { this.id = id; }
        
        public boolean equals(Object o) {
            return o instanceof Key121125 && this.id == ((Key121125) o).id;
        }
        
        public int hashCode() {
            return id;
        }
    }
}

import java.util.concurrent.ConcurrentHashMap;

public class Task131125 {
    public static void main(String[] args) {
        ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>();
        map.put("a", 1);
        map.put("b", 2);
        map.put("c", 3);
        
        int result = map.reduce(2, 
            (k, v) -> k.length() + v, 
            Integer::sum
        );
        
        System.out.println(result);
    }
}

import java.util.HashMap;
import java.util.Map;

public class Task131125 {
    public static void main(String[] args) {
        Map<String, Integer> map = new HashMap<>();
        map.put("a", 1);
        map.put("b", 2);
        
        map.keySet().remove("a");
        map.values().remove(2);
        map.entrySet().removeIf(entry -> entry.getKey().equals("c"));
        
        System.out.println(map.size());
        System.out.println(map.get("a"));
        System.out.println(map.get("b"));
    }
}

import java.util.EnumMap;
import java.util.Map;

enum Color { RED, GREEN, BLUE }

public class Task171125 {
    public static void main(String[] args) {
        Map<Color, String> map = new EnumMap<>(Color.class);
        
        map.put(Color.RED, "red");
        map.put(Color.GREEN, null);
        map.put(null, "null value");
        
        System.out.println(map.get(Color.RED));
        System.out.println(map.get(Color.GREEN));
        System.out.println(map.get(null));
        System.out.println(map.size());
    }
}

import java.util.LinkedHashMap;
import java.util.Map;

public class Task181125 {
    public static void main(String[] args) {
        Map<String, Integer> map = new LinkedHashMap<>(16, 0.75f, true);
        map.put("a", 1);
        map.put("b", 2);
        map.put("c", 3);
        
        map.get("a");
        map.get("b");
        map.put("d", 4);
        map.get("c");
        
        System.out.println(map.keySet());
    }
}

public class Task191125 {
    public static void main(String[] args) {
        Object obj = "42";

        String result = switch (obj) {
            case Integer i -> "Number: " + i;
            case String s when s.length() > 3 -> "Long string";
            case String ignored -> "Short string";
            default -> "Unknown";
        };

        System.out.println(result);
    }
}

public class Task201125 {
    public static void main(String arg) {
        System.out.println("Hello from single arg main");
    }

    public static void main(String[] args) {
        System.out.println("Hello from main");
    }
    
    public static void main() {
        System.out.println("Hello from parameterless main");
    }
}

public class Task211125 {
    public static void main(String[] args) {
        String s1 = "hello";
        String s2 = "he" + "llo";
        String s3 = "he";
        String s4 = "llo";
        String s5 = s3 + s4;
        
        System.out.println(s1 == s2);
        System.out.println(s1 == s5);
        System.out.println(s1.equals(s5));
        
        final String s6 = "he";
        final String s7 = "llo";
        String s8 = s6 + s7;
        System.out.println(s1 == s8);
    }
}