Map HashMap LinkedHashMap IdentiyHashMap WeakHashMap смотреть онлайн

In this Video we discussed about Map and different classes like HashMap, LinkedHashMap, IdentityMap and WeakHashMap which are implementing Map interface.
1./*
* Map: HashMap,LinkedHashMap,IdentiyHashMap,WeakHashMap,SortedMap,NavigableMap,Hashtable,TreeMap
* Set/List: HashSet,LinkedHashSet,SortedSet,NavigableSet,TreeSet
*/
package com.nadboy.collection;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.IdentityHashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.WeakHashMap;

public class MapDemo {

public static void main(String[] args) throws InterruptedException {
// TODO Auto-generated method stub

List ﹤ Employee ﹥ list = new ArrayList ﹤ Employee ﹤ ();
list.add(new Employee());


HashMap ﹤ Integer,String ﹥ map = new HashMap ﹤ Integer, String ﹥ ();
/*
* System.out.println(map.put(1, "ram")); System.out.println(map.put(null,
* "sam")); System.out.println(map.put(null, "pam"));
* System.out.println("map value.."+map);
*/

Hashtable ﹤ Integer,String ﹥ hashtable = new Hashtable ﹤ Integer, String ﹥();

//System.out.println(hashtable.put(1, "ram"));
//System.out.println(hashtable.put(1, "sam"));
//System.out.println(hashtable.put(null, "pam"));
//System.out.println("hashtable value.."+hashtable);
// UpperClass.Innerclass .method()
//EntrySet
Map ﹤ Integer,Employee﹥ employeeMap = new HashMap ﹤ Integer, Employee ﹥();
employeeMap.put(1, new Employee(2, "ram", "[email protected]", 354345345, 45)); //Entry
employeeMap.put(2, new Employee(4, "sam", "[email protected]", 654345345, 25));
employeeMap.put(3, new Employee(5, "pam", "[email protected]", 554345345, 15));
employeeMap.put(4, new Employee(6, "cam", "[email protected]", 454345345, 75));

HashMap ﹤ Integer,Employee ﹥ employeeMap1 = new HashMap ﹤ Integer, Employee ﹥ ();
employeeMap1.putAll(employeeMap);

Iterator ﹤ Employee ﹥ emplist = list.iterator();
Iterator ﹤ Map.Entry ﹤ Integer,Employee ﹥ ﹥ iteratorObj = employeeMap.entrySet().iterator();

//while loop
/*
* while(iteratorObj.hasNext()) { Entry ﹤ Integer,Employee ﹥ entryObj =
* iteratorObj.next(); System.out.println("key..."+entryObj.getKey()
* +"value...."+entryObj.getValue()); }
*/

// for loop
for(Map.Entry ﹤ Integer,Employee ﹥ entryObj: employeeMap.entrySet())
{
// System.out.println("key..."+entryObj.getKey() +"value...."+entryObj.getValue());
}

// forEach
//employeeMap.forEach((k,v) -﹤ {System.out.println("key..."+k +"value..."+v);});

// streams
//employeeMap.entrySet().stream().forEach((item) -﹤ {System.out.println("key..."+item.getKey() +"value.."+ item.getValue());});

Set ﹤ Integer﹥ keys = employeeMap.keySet();
//keys.forEach((k) -﹤ System.out.println("keys.."+k +"value..."+employeeMap.get(k)));
//employeeMap.values().forEach((item) -﹤ System.out.println(item));

LinkedHashMap ﹤ Integer,Employee ﹥ lMapObj = new LinkedHashMap ﹤ Integer,Employee ﹥ ();
lMapObj.put(1, new Employee(2, "ram", "[email protected]", 354345345, 45)); //Entry
lMapObj.put(2, new Employee(4, "sam", "[email protected]", 654345345, 25));
lMapObj.put(3, new Employee(5, "pam", "[email protected]", 554345345, 15));
lMapObj.put(4, new Employee(6, "cam", "[email protected]", 454345345, 75));

//lMapObj.forEach((k,v) -﹤ {System.out.println("key..."+k +"value..."+v);});


IdentityHashMap ﹤ Integer, String ﹥ iHashMap = new IdentityHashMap ﹤ Integer,String ﹥ ();
Map ﹤ Integer,String ﹥ employeeMap2 = new HashMap ﹤ Integer, String ﹥();
Integer i = new Integer(10); //
Integer i1 = new Integer(10);//

iHashMap.put(i, "ram");
iHashMap.put(i1, "sam");

employeeMap2.put(i,"ram");
employeeMap2.put(i1,"sam");

System.out.println(iHashMap); // IdentityHashMap uses == operator for comparison that means it compare the references
System.out.println(employeeMap2); // // HashMap uses equals() method for comparison that means it compare the content.


WeakHashMap ﹤ Employee, String ﹥ wHashMap = new WeakHashMap ﹤ Employee,String ﹥ ();

Employee emp = new Employee(2, "ram", "[email protected]", 354345345, 45);

wHashMap.put(emp,"first Employee");
emp=null;
System.gc();
Thread.sleep(1000);

System.out.println(wHashMap); // Object set with null will be deleted

HashMap ﹤ Employee, String ﹥ hashMap = new HashMap ﹤ Employee,String ﹥();
Employee emp1 = new Employee(2, "ram", "[email protected]", 354345345, 45);
hashMap.put(emp1,"first Employee");
emp1=null;
System.gc();
Thread.sleep(1000);
System.out.println(hashMap); // Object set with null still be available in the case of HashMap




}

}