How to traverse iterate or loop ArrayList in Java (original) (raw)

How to Loop ArrayList in Java

Iterating, traversing or Looping ArrayList in Java means accessing every object stored in ArrayList and performing some operations like printing them. There are many ways to iterate, traverse or Loop ArrayList in Java e.g. advanced for loop, traditional for loop with size(), By using Iterator and ListIterator along with while loop etc. All the method of Looping List in Java also applicable to ArrayList because ArrayListis an essentially List. In next section we will see a code example of Looping ArrayList in Java.

Loop ArrayList in Java – Code Example

Now we know that there are multiple ways to traverse, iterate or loop ArrayList in Java, let’s see some concrete code example to know exactly How to loop ArrayList in Java. I prefer advanced for loop added in Java 1.5 along with Autoboxing,Java Enum, Generics,Varargsand static import, also known as foreach loop if I have to just iterate over Array List in Java. If I have to remove elements while iterating than using Iterator or ListIterator is the best solution.

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

/**
* Java program which shows How to loop over ArrayList in Javausing advanced for loop,
* traditional for loop and How to iterate ArrayList using Iterator in Java
* advantage of using Iterator for traversing ArrayList is that you can remove
* elements from Iterator while iterating.

* @author
*/

public classArrayListLoopExample {

public static voidmain(String args[]) {

//Creating ArrayList to demonstrate How to loop and iterate over ArrayList
ArrayList<**String**> games = new ArrayList<**String**>(10);
games.add("Cricket");
games.add("Soccer");
games.add("Hockey");
games.add("Chess");

System.out.println("original Size of ArrayList : " + games.size());

//Looping over ArrayList in Java using advanced for loop
System.out.println("Looping over ArrayList in Java using advanced for loop");
for(String game: games){
//print each element from ArrayList
System.out.println(game);
}

//You can also Loop over ArrayList using traditional for loop
System.out.println("Looping ArrayList in Java using simple for loop");
for(int i =0; i<games.size(); i++){
String game = games.get(i);
}

//Iterating over ArrayList in Java
Iterator<**String**> itr = games.iterator();
System.out.println("Iterating over ArrayList in Java using Iterator");
while(itr.hasNext()){
System.out.println("removing "+ itr.next()+ " from ArrayList in Java");
itr.remove();
}

System.out.println("final Size of ArrayList : " + games.size());

}

}

Output:
original Size of ArrayList : 4
Looping over ArrayList in Java using advanced for loop
Cricket
Soccer
Hockey
Chess
Looping ArrayList in Java using simple for loop
Iterating over ArrayList in Java using Iterator
removing Cricket from ArrayList in Java
removing Soccer from ArrayList in Java
removing Hockey from ArrayList in Java
removing Chess from ArrayList in Java
final Size of ArrayList : 0

That's all on How to iterate, traverse or loop ArrayList in Java. In summary use advance for loop to loop over ArrayList in Java, its short, clean and fast but if you need to remove elements while looping use Iterator to avoid ConcurrentModificationException.

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