HashMap

Repo to Study HasMap Collection

public class HashMapMain {

public static void main(String[] args) {
	
	HashMap<Integer,String> hashmap = new HashMap<Integer, String>();
	
	//inserting data in hashmap
	
	hashmap.put(1, "First value");
	hashmap.put(2, "Second value");
	hashmap.put(3, "Third value");
	hashmap.put(4, "Fourth value");
	hashmap.put(5, "Fifth value");
	System.out.println("Printing elements in HashMap");
	System.out.println(hashmap);	
	//iterating hashmap
	System.out.println("---------------------------------------------------");
	System.out.println("Printing elements in HashMap using lambda expresion");
	hashmap.forEach(
				(temp,temp1)->{					
					System.out.println("Key: "+ temp + " -----Value: "+ temp1);				
				}			
			);
	System.out.println("---------------------------------------------------");
	System.out.println("Printing elements in HashMap using iterator");
	Iterator iterator = hashmap.entrySet().iterator();
	while (iterator.hasNext()) {
		System.out.println(iterator.next());		
	}
	
	System.out.println("---------------------------------------------------");
	System.out.println("Printing Keys in HashMap using keySet()");
	hashmap.keySet().forEach(System.out::println);
	
	System.out.println("---------------------------------------------------");
	System.out.println("Printing Values in HashMap using values()");
	hashmap.values().forEach(System.out::println);
	
	System.out.println("---------------------------------------------------");
	System.out.println("Get element value by index in hashmap");// start with 1, not 0
	System.out.println(hashmap.get(1));
	
	System.out.println("---------------------------------------------------");
	System.out.println("Get element by value in hashmap");// start with 1, not 0
	Set<Entry<Integer, String>> keyvalue = hashmap.entrySet()
			.stream()
			.filter(a -> a.getValue() == "First value").collect(Collectors.toSet());	
	System.out.println(keyvalue);
	
	System.out.println("---------------------------------------------------");
	System.out.println("Get element by key in hashmap");// start with 1, not 0
	Set<Entry<Integer, String>> value = hashmap.entrySet()
			.stream()
			.filter(a -> a.getKey() == 2).collect(Collectors.toSet());	
	System.out.println(value);
	
	System.out.println("---------------------------------------------------");
	System.out.println("Get element value by key in hashmap");// start with 1, not 0
	String value1 = hashmap.entrySet()
			.stream()
			.filter(a -> a.getKey() == 2)
			.map(a -> a.getValue()).findFirst().orElse("No existe");
	
	System.out.println(value1);
	
	System.out.println("---------------------------------------------------");
	System.out.println("Get element key by value in hashmap");// start with 1, not 0
	int value2 = hashmap.entrySet()
			.stream()
			.filter(a -> a.getValue() == "Second value")
			.map(a -> a.getKey()).findFirst().orElse(0);
	
	System.out.println(value2);

}		

}