There are multiple ways to loop through Map in Java, you can either use foreach loop or Iterator to traverse Map in Java, but all ways use either Set of keys or values for iteration. Since Map by default doesn't guarantee any order, any code which assumes a particular order during iteration will fail. You only want to traverse or loop through a Map, if you want to transform each mapping one by one. Now Java 8 release provides a new way to loop through Map in Java using Stream API and forEach method. For now, we will see 3 ways to loop through each elements of Map. Though Map is an interface in Java, we often loop through common Map implementation like HashMap, Hashtable, TreeMap and LinkedHashMap. By the way, all the ways of traversing Map discussed in this article is pretty general and valid for any Map implementation, including proprietary and third-party Map classes. What I mean by looping through Map is getting mappings one at a time, processing them and moving forward. Let's say, we have a Map of Workers, after appraisal every worker has got 8% hike, now our task is to update this Map, so each worker object reflect its new, increased salary. In order to do this task, we need to iterate through Map, get the Employee object, which is stored as value. Update Worker with new salary, and move on. Did you ask about saving it back to Map? no need; When you retrieve values from Map using get() method, they are not removed from Map, so one reference of same object is always there in Map, until you remove it. That's why, you just need to update object, no need to save it back. By the way, remember to override equals() and hashCode() method for any object, which you are using as key or value in Map. Internal code of  HashMap uses both of these method to insert and retrieve objects into Map, to learn more see How Map works in Java. Now, Let's see how can we loop through Map in Java.