entrySet() – produces a map collection-view whose items are drawn from the Map.Let’s explore what each of these methods does before we use them to iterate through a map: We can iterate over the key and value pairs that are listed below and detailed as follows: Iterator Interface in Java Different Traversal Methods.To follow along with this example, you should be familiar with the following Java programming concepts: In this example, we’ll learn how to iterate over the keys, values, and key/value mappings of a Java HashMap. Internally, it employs a relatively quick hashing technique. Since Java 1.2, hashMap has been a part of the Java collections framework. The Map interface is implemented by the HashMap class, which allows us to store keys. HashMap contains data in (Key, Value) pairs that can be accessed using a different index type. Iteration over an ArrayList-contained HashMap.Iterating through a HashMap with a for loop.Example 3: Iterate through HashMap using the forEach loop.Example 2: Class uses a forEach to iterate through a HashMap.Example 1: Program for traversing Through a HashMap in Java.Example 3: Iterate through HashMap using Iterator ().Example 2: Class for iterating HashMaps using an Iterator.Iterate through HashMap in Java examples.Using Stream API to itrate over entries. Creating a hash map object of key type string and value type integer. The Stream API is a more compact and functional way to iterate over entries. Java 8 introduced Stream API that we can use it to iterate over key-value pairs of HashMap. Hmap.forEach((k,v) -> ("Country: "+ k + ", Capital: " + v)) Ĭountry: New Zealand, Capital: WellingtonĬountry: India, Capital: Delhi Iterate HashMap using Stream API in Java 8 Iteration over map using forEach() method. In this program, we will use lambda expression inside the forEach() method to display each entry of the hash map. ![]() This is the best efficient and simple way. Let’s take an example program based on the forEach() method. Id: 1404, Name: Mark Iterating Java HashMap using forEach() method ("Id: " + entry.getKey() + ", Name: " + entry.getValue()) Iterating over entries of a map using entrySet() method. We will use the following methods for iteration. Let’s take an example program where we will iterate entry of a hash map using Map.Entry method. Iterating Java HashMap using Map.Entrymethod Iterating over values of a hashmap using values() method. Iterating over keys of a hashmap using keySet() method. KeySet() method returns a set view of the keys from a hash map and values() method returns a collection-view of values from a hash map. Let’s take an example program where we will iterate over keys or values of a hash map using keySet() and values() methods. Using keySet(), values(), and for-each loop, you can iterate over keys or values of a hash map. This technique is useful when you want to get a set view of keys or values of a hash map. Iterating over keys or values using keySet() and value() methods ("Entries of HashMap after removing: " +hmap.entrySet()) Įntries of HashMap after removing: ![]() Itr.remove() // This method will remove the last entry of a hash map while iterating. Removing the last entry returned by Iterator Here, entrySet is a method that is used to get a view of entries of a map. Let’s take another example where we will remove the last entry of a hash map returned by the Iterator. Iterator itr3 = hmap.values().iterator() values is a method that is used to get values of keys of a hash map. Iterator itr2 = hmap.keySet().iterator() keySet is a method that is used to get view of keys of a hash map. Iterator> itr = hmap.entrySet().iterator() entrySet is a method that is used to get view of entries of a hash map. Creating an Iterator object using iterator() method. HashMap hmap = new HashMap() // Creating a hash map. Let’s take an example program where we will iterate hash map in java using java iterator concept. Let’s understand all the important ways to iterate HashMap in Java.
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