import java.util.Optional;

public class Task011125 {
    public static void main(String[] args) {
        Optional<String> opt1 = Optional.ofNullable(null);
        Optional<String> opt2 = Optional.of("java");
        
        String result1 = opt1.or(()-> opt2).orElse("default");
        String result2 = opt2.filter(s -> s.length() > 10)
                           .or(()-> Optional.of("fallback"))
                           .get();
        
        System.out.println(result1);
        System.out.println(result2);
    }
}

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

public class Task041125 {
    public static void main(String[] args) {
        Map<String, Integer> map = new HashMap<>();
        
        String key = "key";
        System.out.print(map.put(key, 1) + " ");
        System.out.print(map.put(key, 2) + " ");
        System.out.print(map.putIfAbsent(key, 3) + " ");
        System.out.print(map.compute(key, (k, v) -> null) + " ");
        System.out.print(map.put(key, 4));
    }
}

import java.util.TreeMap;

public class Task061125 {
    public static void main(String[] args) {
        TreeMap<Integer, String> map = new TreeMap<>();
        map.put(1, "one");
        map.put(3, "three");
        map.put(5, "five");
        map.put(7, "seven");
        
        System.out.print(map.lowerKey(4) + " ");
        System.out.print(map.floorKey(4) + " ");
        System.out.print(map.higherKey(4) + " ");
        System.out.print(map.ceilingKey(4));
    }
}

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

public class Task051125 {
    public static void main(String[] args) {
        Map<String, Integer> map = new HashMap<>();
        map.put("a", 1);
        map.put("b", 2);
        map.put("c", null);
        
        Integer value1 = map.get("a");
        Integer value2 = map.get("c");
        Integer value3 = map.get("d");
        int value4 = map.getOrDefault("d", -1);
        
        System.out.println(value1);
        System.out.println(value2);
        System.out.println(value3);
        System.out.println(value4);
    }
}

import java.util.concurrent.ConcurrentHashMap;

public class Task071125 {
    public static void main(String[] args) throws InterruptedException {
        ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>();
        map.put("count", 0);

        Thread t1 = new Thread(() -> {
            for (int i = 0; i < 1000; i++) {
                map.computeIfPresent("count", (k, v) -> v + 1);
            }
        });

        Thread t2 = new Thread(() -> {
            for (int i = 0; i < 1000; i++) {
                map.put("count", map.get("count") + 1);
            }
        });

        t1.start();
        t2.start();
        t1.join();
        t2.join();

        System.out.println(map.get("count"));
    }
}

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

public class Task101125 {
    public static void main(String[] args) {
        Map<Integer, String> map = new HashMap<>();
        map.put(1, "one");
        map.put(2, "two");
        map.put(3, "three");
        
        String result1 = map.remove(2);
        String result2 = map.remove(4);
        boolean result3 = map.remove(1, "two");
        boolean result4 = map.remove(3, "three");
        
        System.out.println(result1);
        System.out.println(result2);
        System.out.println(result3);
        System.out.println(result4);
    }
}

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

public class Task111125 {
    public static void main(String[] args) {
        Map<String, Integer> map = new HashMap<>();
        map.put("a", 1);
        map.put("b", 2);
        map.put("c", null);
        
        map.merge("a", 10, (oldVal, newVal) -> null);
        map.merge("b", 20, (oldVal, newVal) -> oldVal + newVal);
        map.merge("c", 30, (oldVal, newVal) -> oldVal + newVal);
        map.merge("d", 40, (oldVal, newVal) -> oldVal + newVal);
        
        System.out.println(map.get("a"));
        System.out.println(map.get("b"));
        System.out.println(map.get("c"));
        System.out.println(map.get("d"));
    }
}

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;
        }
    }
}