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Byron is a master software engineer working in the IT and Telecom domains. He is an applications developer in a wide variety of applications/services. He is currently acting as the team leader and technical architect for a proprietary service creation and integration platform for both the IT and Telecom industries in addition to a in-house big data real-time analytics solution. He is always fascinated by SOA, middleware services and mobile development. Byron is co-founder and Executive Editor at Java Code Geeks.

Safe collection iteration example

In this example we shall show you how to obtain a safe Collection iteration. We are using the List implementation of Collection, but the Collections API provides methods for such operations in other Collection implementations too, such as Map and Set. To obtain a safe Collection iteration one should perform the following steps:

  • Call synchronizedList(List list) API method of Collections to get a synchronized (thread-safe) list.
  • Add elements to the list, using add(Object e) API method of List.
  • Set the list in a synchronized statement and then iterate through its elements, using the iterator() API method of the List and hasNext(), next() API methods of Iterator,

as described in the code snippet below.

package com.javacodegeeks.snippets.core;

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

public class SafeCollectionIteration extends Object {

    public static void main(String[] args) {

  List words = Collections.synchronizedList(new ArrayList());





  synchronized (words) {

Iterator it = words.iterator();

while (it.hasNext()) {


    String str = (String) it.next();

    System.out.println("" + str + ", characters="+ str.length());




JavaCodeGeeks, characters=13
is, characters=2
very, characters=4
cool!, characters=5

This was an example of how to obtain a safe Collection iteration in Java.

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