![]() ![]() Feel free to hop back or post questions whenever you feel stuck. You are encouraged to practise these and try out other methods of traversal as well. Use the for-each loop if you have nested loops (to avoid complexity).ĬonclusionBy the end of the post, we hope you have learned how to iterate map in Java.User the iterator if you have to modify the map.Which traversal method to use and when?If you are not sure whether to use the for-each or the iterators to iterate your map, then you can take the following suggestions. Hence, you don’t have the access to modify or delete any data. The reason for this is that the for-each loop implicitly creates an iterator, that is not exposed to the user. Contrarily, if you try to edit/delete map data using the for-each loop, it will throw a ConcurrentModificationException. The steps we followed in the below example are as follows: 1) Create a HashMap and populate it with key-value pairs. In this example we are gonna see how to iterate a HashMap using Iterator and display key and value pairs. The iterators class facilitates you by providing implementation to edit/remove the data in the map. In the previous tutorial we have seen different-2 ways to iterate a HashMap. On the contrary, you can easily modify data using iterators. What is the difference between the two methods?The for-each loop does not allow to update/modify the data in the map. So none is better than the other, it depends on what you need to use and when. In terms of performance, both for-each loop and the iterators have the same time complexity. Is the Foreach loop better than the iterators method?It does not matter which method you use for the traversal of a map as long as it does the job for you. There you go! Your traversal is complete, just like that. Now traverse the map while keep checking the next entity that exists on the map. First, you need to import the iterator class, and then get the iterator for the entrySet. Key = 10, value = October ExplanationIn this example, we create explicit iterator to traverse / iterate over the map. Iterator> iterator = monthsInAYear.entrySet().iterator() iterate map / traverse the map using using iterator As an exercise, you can explore the rest of the methods to strengthen your command on this concept. Here, we have only used getKey() and getValue() to display the data on the console. Where you can use all the methods of Map.Entry as per your requirements. The iterator will run through each element in. Each entrySet contains a key and corresponding values. You can use the HashMap keys, HashMap values, and HashMap Entry Object to iterate over the HashMap in Java. By using the for-each loop, we get an entrySet() which provides an automated “view” of the data in the map, in the form of key-value pairs. Key = 5, value = Friday ExplanationIn this example we used the foreach loop to iterate over the map. ![]() ("key = " + entry.getKey() + ", value = " + entry.getValue()) Iterating over the Map.entrySet() using map.forEachįor (Map.Entry entry : businessDays.entrySet()) store business days i-e key/value pairs in the Map Please find the implementation of both methods below. However, we will focus on the most efficient and simple ways. What are some common ways to iterate a Map in Java?Though there are many ways to traverse a map. Let’s explore some of the options we have. Note: We can also use the HashMap forEach() method to iterate over the hashmap.Why do we need to iterate through a Map?We need to traverse or iterate over a map for accessing, modifying or removing data.
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