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package collectionspractice;

import java.util.HashMap;

import java.util.Map;

public class HashMapPractice{

private final HashMap<Integer, Integer> hashMap= new HashMap<>();

void learnHashMap(){

hashMap.put(1, 10);

hashMap.put(2, 20);

hashMap.put(3, 30);

hashMap.put(4, 40);

System.out.println("hashmap get " + hashMap.get(3));

System.out.println("hashmap contains key " + hashMap.containsKey(2));

System.out.println("hashmap contains value " + hashMap.containsValue(10));

hashMap.remove(3);

int mapSize = hashMap.size();

//hashMap.clear();

System.out.println("is empty" + hashMap.isEmpty());

//loops

for (int key : hashMap.keySet()){

System.out.print(key + " key\t");

}

for (int key : hashMap.values()){

System.out.print(key + " value\t");

}

for(Map.Entry<Integer, Integer> entry : hashMap.entrySet()){

System.out.println("entry key and value - " + entry.getKey() + " " + entry.getValue());

}

System.out.println(hashMap.getOrDefault(3, 0));

System.out.println(hashMap);

hashMap.replace(2, 21); // replace if key exists

System.out.println(hashMap);

hashMap.replace(2, 21, 20); // replace only if oldValue matches

System.out.println(hashMap);

hashMap.putIfAbsent(2, 40); // only puts if key is missing

System.out.println(hashMap);

hashMap.replace(2, 31, 20); // replace only if oldValue matches

System.out.println(hashMap);

hashMap.putIfAbsent(9, 20);

System.out.println(hashMap);

}

}