.map in java code example

Example 1: map java

import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;


public class Main {
   public static void main(String[] args) {

      //La fameuse syntaxe en diamant de Java 7
      Map<Integer, String> hm = new HashMap<>();
      hm.put(10, "1");
      hm.put(20, "2");
      hm.put(30, "3");
      hm.put(40, "4");
      hm.put(50, "5");
      //Ceci va écraser la valeur 5
      hm.put(50, "6");
      
      System.out.println("Parcours de l'objet HashMap : ");
      Set<Entry<Integer, String>> setHm = hm.entrySet();
      Iterator<Entry<Integer, String>> it = setHm.iterator();
      while(it.hasNext()){
         Entry<Integer, String> e = it.next();
         System.out.println(e.getKey() + " : " + e.getValue());
      }
      
      System.out.println("Valeur pour la clé 8 : " + hm.get(8));
      
      Map<Integer, String> lhm = new LinkedHashMap<>();
      lhm.put(10, "1");
      lhm.put(20, "2");
      lhm.put(30, "3");
      lhm.put(40, "4");
      lhm.put(50, "5");
      
      System.out.println("Parcours de l'objet LinkedHashMap : ");      
      Set<Entry<Integer, String>> setLhm = lhm.entrySet();
      Iterator<Entry<Integer, String>> it2 = setLhm.iterator();
      while(it2.hasNext()){
         Entry<Integer, String> e = it2.next();
         System.out.println(e.getKey() + " : " + e.getValue());
      }
   }
}

Example 2: map in java

MAP : is a (key-value format) 
      and keys are always unique, 
      and value can be duplicated. 
- HashTable don't have null key, sychronized(thread-safe)
- LinkedHashMap can have null key, keeps order
- HasHMap can have null key, order is not guaranteed
- TreeMap doesn't have null key and keys are sorted

Example 3: java map declaration

Map< String,Integer> hm =  
                        new HashMap< String,Integer>(); 
       hm.put("a", new Integer(100)); 
       hm.put("b", new Integer(200)); 
       hm.put("c", new Integer(300)); 
       hm.put("d", new Integer(400));