import java.util.ArrayList;
import java.util.List;

class ArraylistDemo
{
	public static void main(String s1[])
	{
		ArrayList list =new ArrayList();//creating object of ArrayList
    	//adding elements to ArrayList
    	list.add("user1");
    	list.add("user2");
    	list.add("user3");
    	list.add("user4");
    	System.out.println(list);
    }
}

[user1, user2, user3, user4]

import java.util.ArrayList;
import java.util.List;

class ArraylistDemo
{
	public static void main(String s1[])
	{
		ArrayList list =new ArrayList();//creating object of ArrayList
    	//adding elements to ArrayList
    	list.add("user1");
    	list.add("user2");
    	list.add("user3");
    	list.add("user4");
    	System.out.println(list);
    	//size() calculate size of ArrayList
    	System.out.println("Total number of element= "+list.size());
    }
}
		

Output
[user1, user2, user3, user4]
Total number of element= 4

      

import java.util.ArrayList;
import java.util.List;

class ArraylistDemo
{
	public static void main(String s1[])
	{
		//1- create Arraylist
		List list=new ArrayList();
		list.add("user1");
		list.add("user2");
		list.add("user3");
		list.add("user4");
		
		//2- print ArrayList 
		System.out.println("original list ="+list);
		
		//3- update ArrayList
		list.set(1,"updated user");
		System.out.println("After update list = "+list);
		
		//4-deleting element in ArrayList
		list.remove(1);
		list.remove("user1");
		System.out.println("After deletion list = "+list);
	}
}

original list =[user1, user2, user3, user4]
After update list = [user1, updated user, user3, user4]
After deletion list = [user3, user4]

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class ListIterator {
	/**
	*we can iterate ArrayList by three ways
	*1- By using get(int index) method
	*2- By using Iterator
	*3- By using enhanced for-loop
	*/
	public static void main(String[] args) {
		List list=new ArrayList();
		list.add("user1");
		list.add("user2");
		list.add("user3");
		list.add("user4");
		list.add("user5");
		System.out.println("first method");
		for(int i=0;i<(list.size());i++)	//simple for-loop
		{
			System.out.println(list.get(i));	//get() method
		}
		System.out.println("second method");
		Iterator i=list.iterator();	//Iterator class
		while(i.hasNext())
		{
			System.out.println(i.next());
		}
		System.out.println("third method");
		for(Object o:list)	//enhanced for-loop
		{
			System.out.println(o);
		}
	}
}

first method
user1
user2
user3
user4
user5
second method
user1
user2
user3
user4
user5
third method
user1
user2
user3
user4
user5

import java.util.List;
import java.util.Vector;

class VectorDemo
{
	public static void main(String s1[])
	{
		//1- create Vector
		Vector list=new Vector();
		list.add("user1");
		list.add("user2");
		list.add("user3");
		list.addElement("user4");//another add method
		
		//2- print Vector 
		System.out.println("original list ="+list);
		
		//3- update Vector
		list.set(1,"updated user");
		System.out.println("After update list = "+list);
		
		//4-deleting element in Vector
		list.remove(1);
		list.remove("user1");
		System.out.println("After deletion list = "+list);
	}
}

original list =[user1, user2, user3, user4]
After update list = [user1, updated user, user3, user4]
After deletion list = [user3, user4]

import java.util.LinkedList;
import java.util.List;

class LinkedListDemo
{
	public static void main(String s1[])
	{
		//1- create LinkedList
		LinkedList list=new LinkedList();
		list.add("user1");
		list.add("user2");
		list.add("user3");
		list.addFirst("first user");
		list.addLast("last user");
		
		//2- print LinkedList 
		System.out.println("original list ="+list);
		System.out.println("first element in list is = "+list.getFirst());
		System.out.println("last element in list is = "+list.getLast());
		
		//3- update LinkedList
		list.set(1,"updated user");
		System.out.println("After update list = "+list);
		
		//4-deleting element in LinkedList
		list.remove(1);
		list.remove("user1");
		list.removeFirst();
		list.removeLast();
		System.out.println("After deletion list = "+list);
		list.removeAll(list);	//delete all element from list
	}
}

original list =[first user, user1, user2, user3, last user]
first element in list is = first user
last element in list is = last user
After update list = [first user, updated user, user2, user3, last user]
After deletion list = [user2, user3]

import java.util.Collections;
import java.util.LinkedList;
import java.util.List;

class SortingDemo
{
	public static void main(String s1[])  
    {  
        List list=new LinkedList();  
        list.add("peter");  
        list.add("john");  
        list.add("alina");  
        System.out.println("Before sorting = "+list);  
        Collections.sort(list);  
        System.out.println("After sorting  = "+list);     
    }  
}

 

Before sorting = [peter, john, alina]
After sorting  = [alina, john, peter]

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;


public class SortDemo implements Comparable{
	Integer cid;
	String name;
	String add;
	public SortDemo()
	{}
	public SortDemo(Integer cid,String name,String add)
	{
		this.cid=cid;
		this.name=name;
		this.add=add;
	}
	public boolean equals(Object o)
	{
		boolean result =false;
		SortDemo sortDemo=(SortDemo)o;
		if(this.cid.equals(sortDemo.cid))
		{
			return true;
		}
		return result;
		
	}
	public String toString()
	{
		return "cid = "+cid+"\nname = "+name+"\nadd = "+add+"\n";
	}
	public int compareTo(Object o)
	{
		int k;
		SortDemo sortDemo=(SortDemo)o;
		k=this.name.compareToIgnoreCase(sortDemo.name); //this will sort by name
		return k;
	}
	public static void main(String[] args) {
		SortDemo s1=new SortDemo(100,"parker","MRT");
		SortDemo s2=new SortDemo(89,"john","delhi");  
		SortDemo s3=new SortDemo(102,"smith","delhi");  
		List list=new ArrayList();
		list.add(s1);
		list.add(s2);
		list.add(s3);		
		Collections.sort(list);
		System.out.println(list);
	}
}

 

[cid = 89 name = john add = delhi , cid = 100 name = parker add = MRT , cid = 102 name = smith add = delhi ]

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;

class SortByName implements Comparator {
	
	public int compare(Object o1,Object o2)
	{
		TestComparator tc1=null;
		TestComparator tc2=null;
		int z=0;
		if(o1 instanceof TestComparator && o2 instanceof TestComparator)
		{
			tc1=(TestComparator)o1;
			tc2=(TestComparator)o2;
			z=tc1.name.compareToIgnoreCase(tc2.name);
			
		}
		return z;
	}

}
public class TestComparator {
	Integer cid;
	String name;
	String add;
	TestComparator(Integer cid,String name,String add)
	{
		this.cid=cid;
		this.name=name;
		this.add=add;
	}
	
	@Override
	public String toString() {
		return "TestComparator [cid=" + cid + ", name=" + name + ", add=" + add
				+ "]";
	}
	public static void main(String[] args) {
		TestComparator cd=new TestComparator(1001,"shalabh","canada");
		TestComparator cd1=new TestComparator(2001,"yutika","london");
		ArrayList list=new ArrayList();
		list.add(cd1);
		list.add(cd);
		Collections.sort(list,new SortByName());
		System.out.println(list);
	}
}
 

[TestComparator [cid=1001, name=shalabh, add=canada], TestComparator [cid=2001, name=yutika, add=london]]

     
       import java.util.List;
import java.util.Vector;

class SearchDemo
{
	public static void main(String s1[])
	{
		List list=new ArrayList();
		list.add("user1");
		list.add("user2");
		list.add("user3");
		list.add("user4");
		list.add("user5");
		list.add("user1");
		boolean contain = list.contains("user2");
		System.out.println(contain);
		int index =list.indexOf("user4");
		System.out.println("index is = "+index);
		int lastIndex = list.lastIndexOf("user1");
		System.out.println("Last Index = "+lastIndex);
	}
}
      
 

true
index is = 3
Last Index = 5

import java.util.LinkedHashSet;
import java.util.Set;

public class LinkedHashSetDemo{
	
	public static void main(String[] args) {
	//it don't allow duplicate element and it allow order
		Set set=new LinkedHashSet();	
		set.add("user1");
		set.add("user2");
		set.add("user3");
		set.add("user5");
		set.add("user4");
		set.add("user5");// remove duplicate element
		set.add("user5");
		System.out.println("List with No duplicate element = "+set);
	}
}

 

List with No duplicate element = [user1, user2, user3, user5, user4]

import java.util.HashSet;
import java.util.Set;
public class Demo {
	public static void main(String[] args) {
		//it don't allow duplicate element and no order
			Set set=new HashSet();	
			set.add("user1");
			set.add("user2");
			set.add("user3");
			set.add("user5");
			set.add("user4");
			set.add("user5");
			set.add("user5");
			System.out.println("List with No duplicate element = "+set);
		}
}

 

List with No duplicate element = [user1, user2, user3, user5, user4]

import java.util.Set;
import java.util.TreeSet;

public class TestComparator {
	
	public static void main(String[] args) {
	//it allow pre-sorted and no duplcate element
		Set set=new TreeSet();	
		set.add("user1");
		set.add("user2");
		set.add("user3");
		set.add("user5");
		set.add("user4");
		set.add("user5");
		set.add("user5");
		System.out.println("List with No duplicate element = "+set);
	}
}

 

List with No duplicate element = [user1, user2, user3, user4, user5]

import java.util.HashSet;  
import java.util.Set;  
import java.util.TreeSet;  
/** 
To avoid duplicate values from HashSet you have to override  
hashCode and equals method 
*/  
public class Demo {  
    String name;  
    String address;  
    Integer id;  
    public Demo(String name, String address,Integer id)  
    {  
        this.name=name;  
        this.address=address;  
        this.id=id;  
    }  
    public String toString()  
    {  
        return "name ="+name+" address = "+address+" id = "+id;   
    }  
    public boolean equals(Object o)  
    {  
    	Demo demo=null;  
        if(o instanceof Demo)  
        {  
        	demo=(Demo)o;  
            if(this.name.equals(demo.name))  
            {  
                return true;  
            }  
        }  
        return false;  
    }  
    public int hashCode()  
    {  
        return this.name.length()*5;  
    }  
    public static void main(String[] args) {  
    	Demo hsd1=new Demo("john","delhi",1001);  
    	Demo hsd2=new Demo("alia","delhi",1002);  
    	Demo hsd3=new Demo("peter","mrt",2000);  
    	Demo hsd4=new Demo("john","delhi",1001);  
        Set hash=new HashSet();  
        hash.add(hsd1);  
        hash.add(hsd2);  
        hash.add(hsd3);  
        hash.add(hsd4);  
        System.out.println("list with no duplicate object "+ hash);     
    }  
}  

 

list with no duplicate object [name =alia address = delhi id = 1002, name =john address = delhi id = 1001, name =peter address = mrt id = 2000]

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MapDemo {
	
	public static void main(String[] args) {
		Map map=new HashMap();//creating object of HashMap
    	//adding elements to HashMap
    	map.put("name","peter");
    	map.put("address","delhi");
    	map.put("age", 22);
    	System.out.println(map);
	}
}
 

{address=delhi, age=22, name=peter}

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MapDemo {
	
	public static void main(String[] args) {  
        Map map = new HashMap();  
        List peterPhone = new ArrayList();  
        peterPhone.add(99999);  
        map.put("peter",peterPhone);  
        List ramPhone = new ArrayList();  
        ramPhone.add(8888);  
        ramPhone.add(7777);  
        ramPhone.add(6666);  
        map.put("ram",ramPhone);  
        System.out.println("Map is "+map);  
        System.out.println("pater Value is "+map.get("peter"));  
        System.out.println("Ram Value is "+map.get("ram"));  
    }  
}

 

Map is {ram=[8888, 7777, 6666], peter=[99999]}
pater Value is [99999]
Ram Value is [8888, 7777, 6666]

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
class Customer{
	String name;
	String age;
	int cid;
	Customer(String name,String age,int cid){
		this.name=name;
		this.age=age;
		this.cid=cid;
	}
	@Override
	public String toString() {
		return "Customer [name=" + name + ", age=" + age + ", cid=" + cid + "]";
	}
	
}
class Address{
	String streetNo;
	String city;
	Address(String streetNo,String city){
		this.streetNo=streetNo;
		this.city=city;
	}
	@Override
	public String toString() {
		return "Address [streetNo=" + streetNo + ", city=" + city + "]";
	}
	
}
public class NestedMapDemo {
	
	public static void main(String[] args) {
		Customer peter=new Customer("peter", "22",101);
		Customer smith=new Customer("smith", "23",102);
		Address officeAdd=new Address("107", "delhi");
		Address resendialAdd=new Address("108","gurgoan");
		
		Map customer=new HashMap();
		customer.put("peter",peter);
		customer.put("smith",smith);
		
		Map address=new HashMap();
		address.put("officeAdd",officeAdd);
		address.put("resendialAdd", resendialAdd);
		
		Map mainMap=new HashMap();
		mainMap.put("customer",customer);
		mainMap.put("address",address);
		System.out.println(mainMap);
	}
}
 

{address={officeAdd=Address [streetNo=107, city=delhi], resendialAdd=Address [streetNo=108, city=gurgoan]}, customer={peter=Customer [name=peter, age=22, cid=101], smith=Customer [name=smith, age=23, cid=102]}}

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
public class Customer {
	Integer cid;
	String name;
	String address;
	Customer(Integer cid,String name,String address){
		this.cid=cid;
		this.name=name;
		this.address=address;
	}
	@Override
	public String toString() {
		return "Customer [cid=" + cid + ", name=" + name + ", address="
				+ address + "]";
	}
	public static void main(String[] args) {
		Customer customer=new Customer(1001,"peter","New york");
		Customer customer1=new Customer(1002,"john" ,"Pak");
		List list =new ArrayList();
		list.add(customer);
		list.add(customer1);
		Iterator i=list.iterator();
		while(i.hasNext()){
			System.out.println(i.next());
		}
	}
}

 

Customer [cid=1001, name=peter, address=New york]
Customer [cid=1002, name=john, address=Pak]

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MapDemo {
	
	public static void main(String[] args) {  
        Map map = new HashMap();  
        List peterPhone = new ArrayList();  
        peterPhone.add(99999);  
        map.put("peter",peterPhone);  
        List ramPhone = new ArrayList();  
        ramPhone.add(8888);  
        ramPhone.add(7777);  
        ramPhone.add(6666);  
        map.put("ram",ramPhone);  
        System.out.println("Map is "+map);  
        System.out.println("pater Value is "+map.get("peter"));  
        System.out.println("Ram Value is "+map.get("ram"));  
    }  
}

 

Map is {ram=[8888, 7777, 6666], peter=[99999]}
pater Value is [99999]
Ram Value is [8888, 7777, 6666]

import java.util.ArrayList;  
import java.util.List;  
public class WildcardDemo {  
    //As it is a unbounded wildcard it can take anything  
    public void print(List<?> list)     
    {  
        System.out.println(list);  
    }  
    public static void main(String[] args) {  
        List<String> string = new ArrayList<String>();  
        List<Integer> integer=new ArrayList<Integer>();  
        string.add("hi");  
        string.add("hello");  
        string.add("bye");  
          
        integer.add(111);  
        integer.add(222);  
        integer.add(333);  
        WildcardDemo wd=new WildcardDemo();  
        wd.print(string);  
        wd.print(integer);   
    }  
}  

 

[hi, hello, bye]
[111, 222, 333]

import java.util.ArrayList;  
import java.util.List;  
public class WildcardDemo {  
    //As it is a unbounded wildcard it can take anything  
	public void print(List<? extends Number> list)	
	{
		System.out.println(list);
	}  
    public static void main(String[] args) {  
        List<String> string = new ArrayList<String>();  
        List<Integer>integer=new ArrayList<Integer>();  
        string.add("hi");  
        string.add("hello");  
        string.add("bye");  
          
        integer.add(111);  
        integer.add(222);  
        integer.add(333);  
        WildcardDemo wd=new WildcardDemo();  
       	wd.print(string);  //compile time error
        wd.print(integer);   
    }  
}   

 

Complie time error

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Vector;
/**
 * @author shalabh
 * we know that Vector is synchronized but ArrayList 
 * is not synchronized ,to make ArrayList synchronized
 * we 
 */
public class ArrayListTheadSafeDemo {   
    public static void main(String[] args) {  
    	Listlist = Collections.synchronizedList(new ArrayList<String>());
    	list.add("user1");
    	list.add("user2");
    	list.add("user3");
		// when iterating over a synchronized list, we need to synchronize access to the synchronized list
		synchronized (list) {	// Must be in synchronized block
			Iterator<String> iterator = list.iterator();
			while (iterator.hasNext()) {
				System.out.println(iterator.next());
			}
		}
    }  
}  

 

user1
user2
user3

import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

public class HashSetTheadSafeDemo {   
    public static void main(String[] args) {  
    	Set<String> set = Collections.synchronizedSet(new HashSet<String>());
    	set.add("user1");
    	set.add("user2");
    	set.add("user3");
		// when iterating over a synchronized set, we need to synchronize access to the synchronized set
		synchronized (set) {
			Iterator<String> iterator = set.iterator();
			while (iterator.hasNext()) {
				System.out.println(iterator.next());
			}
		}
    }  
}  

 

user2
user1
user3