How to iterate through list in java

List is a collection in java used to store Ordered objects which can be duplicate. List can be used to store either primitive data type or instances of a defined class. how to store object /instance of a class you can read here.

There are 4 different ways to iterate through a list:

1. With for loop

2. Using advanced for loop

3. using iterator or list iterator

4. using do-while loop

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Using for Loop

The basic loop can be used to iterate through a list 

Example : Suppose we have a list of car which includes name of cars .Names can be retrieved with the help of for loop 

package test;

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

public class MainS {


public static void main(String[] args) {



List carNames= new ArrayList();
carNames.add("skoda");
carNames.add("bmw");
carNames.add("jaguar");
for (int i = 0; i < carNames.size(); i++) {
System.out.println(carNames.get(i));
}

}
See :How to sort an Array List without using Comparator or sort method

2. Using advanced for loop

package test;

import java.util.ArrayList;

import java.util.List;

public class testing {

    public static void main(String[] args) {

         List carNames= new ArrayList();

           carNames.add("skoda");

           carNames.add("bmw");

           carNames.add("jaguar");

    for(Object l :carNames)  

    {

         System.out.println(l);

          

    }

          

         }

    }

   

    Working :

for(Object l :carNames)  

    {

         System.out.println(l);

          

    }

Here we took List carNames= new ArrayList();

CarNames list is not of any specific datatype means String ,Integer etc so its storing objects with value skoda,bmw etc.

So while reteriving we used for(Object l :carNames)to retrieve elements.

If you use for(String l :carNames)then it will compilation error because carNames list contains object elements not of String or any other datatype.

If you want to retrieve using a datatype then you must need to specify datatype while declaring the list as

List<String> carNames= new ArrayList<String> ();

                                      OR

List<Integer> carNames= new ArrayList<Integer> ();

                 OR

ArrayList<String> carNames= new ArrayList<String> ();

                                           OR

Whatever you want :D

Then you can retrieve elements as

 for(String l :carNames)

         OR

for(Integer l :carNames)

         

This is very normal …. I want to do something very cool like want to store all type of data objects in one list not a single Generic type.

Like I want to store Integer ,String, Object of a class in one list … yeahhh J

Following is the example for the same :

package test;

import java.util.ArrayList;

import java.util.List;

public class testing {

    public static void main(String[] args) {

         List<Object> carNames= new ArrayList<Object>();

/* Or List carNames= new ArrayList();

           carNames.add(new Integer(1));

           carNames.add(new String("Hello"));

           carNames.add("jaguar");

           carNames.add(new Double(10.5));

    for(Object l :carNames)  

    {

         System.out.println(l);

          

    }

          

         }

    }

   

   

That’s coolll !!!!

Output :

1
Hello
jaguar
10.5

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Using Iterator :

package test;

import java.util.ArrayList;

import java.util.List;

public class testing {

    public static void main(String[] args) {

         List<Object> carNames= new ArrayList<Object>();

/* Or List carNames= new ArrayList();

           carNames.add(new Integer(1));

           carNames.add(new String("Hello"));

           carNames.add("jaguar");

           carNames.add(new Double(10.5));
Iterator i= carNames.iterator;

    while(i.hasnext())  

    {

         System.out.println(i.next());

          

    }

          

         }

    }

   

using do-while loop :

package test;

import java.util.ArrayList;

import java.util.List;

public class testing {

    public static void main(String[] args) {

         List<Object> carNames= new ArrayList<Object>();

/* Or List carNames= new ArrayList();

           carNames.add(new Integer(1));

           carNames.add(new String("Hello"));

           carNames.add("jaguar");

           carNames.add(new Double(10.5));
Iterator i= carNames.iterator;

      do

    {

         System.out.println(i.next());

          

    }while(i.hasnext())

          

         }

    }

See also :
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