In this article, we will see how to print HashMap in java using different method.
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Table of Contents<\/p>
This is the most basic and easiest method to print out HashMap in java<\/a>. Pass the HashMap reference to the System.out.println<\/a>, and the HashMap will output the key-value of the elements enclosed in curly brackets.<\/p>\n We will use a HashMap constructor<\/a> and a pass A Map is an interface that forms the basis for all map implementations, including a HashMap. The If there are any duplicate keys, the method throws Output:<\/p>\n The HashMap To get the key for every value in the HashMap, we use a for-loop with the The key set method returns a set of unique keys, and we pass the keys to the get method to retrieve each value.<\/p>\n Output:<\/p>\n To use Consumer functional interface<\/a>, you have to use the Since the The forEach()<\/a> is a method from the The for-each method iterates through the elements in the HashMap until they are exhausted as it prints them out using System.out.println.<\/p>\n Output:<\/p>\n To print out the elements of a HashMap using this class, pass the HashMap reference to the This method will print out a list of elements in the HashMap as an Array.<\/p>\n When the reference of the array is is Output:<\/p>\n The When you try to add or remove elements from the singleton list it throws an The Output:<\/p>\n To use the The map entry contains the key-value elements in the HashMap, and the elements are only available during the iteration period.<\/p>\n Since A for loop<\/a> will iterate through the elements in the Set of Map entries and print out the key for each value using the get key method and the value using the get value method.<\/p>\n Output:<\/strong><\/p>\n BiConsumer<\/a> is a Functional Interface that represents an operation that accepts two arguments and returns no value.<\/p>\n The BiConsumer functional interface<\/a> is a parameter of the The type declared in the HashMap is the only type of value that will be accepted by the The functional interface will use the The action of our consumer will be printing out the elements in the HashMap. Note that if the action is null or an entry is removed during iteration, the for-each method will throw a NullPointerException<\/a> and Output:<\/p>\n We can access the Since the Set class inherits from the Iterable interface we can return an Iterator<\/a> then use the The Output:<\/p>\nMap<\/code> of elements to the constructor, which provides an easier way to initialize a HashMap with values using the Map.of()<\/code> method.<\/p>\nMap.of()<\/code> method returns an unmodifiable map containing the number of elements you create.<\/p>\nIllegalArgumentException<\/code> and a NullPointerException<\/a> if any key or value is null<\/code>.<\/p>\n\npublic static void main(String[] args) {\n HashMapPrint HashMap using foreach method with keyset()<\/span><\/h2>\n
get(Object key)<\/code> is a method that returns the value that belongs to a particular key.<\/p>\nkeySet()<\/code> method.<\/p>\n\npublic static void main(String[] arg){\n HashMap
\n2 = john@domain.com
\n3 = jane@domain.com\n<\/div>\nPrint HashMap using Consumer with entrySet()<\/span><\/h2>\n
entrySet()<\/code> method, which returns a Set<\/code> containing the same type of key-value elements.<\/p>\nSet<\/code> is a Collection<\/code> class that implements Iterable<\/code>, use the forEach()<\/code> method to print out the elements of the HashMap.<\/p>\nIterable<\/code> class, and it accepts only a Consumer as the parameter.<\/p>\n\npublic static void main(String[] arg){\n HashMap
\n2=B
\n3=C
\n4=D\n<\/div>\nPrint HashMap using Arrays’s asList() method<\/span><\/h2>\n
asList()<\/code> method of the Arrays<\/code> class.<\/p>\nnull<\/code>, it throws a NullpointerException<\/a> except where noted.<\/p>\n\npublic static void main(String[] arg){\n HashMapPrint HashMap using Collections’s singletonList()<\/span><\/h2>\n
singletonList()<\/code> is a static method from the Collections<\/code> class hence no instantiation is required to use the method.<\/p>\nsingletonList()<\/code> returns an immutable<\/a> list which is simply a list that can not be modified by either adding or removing elements from it once it has been created.<\/p>\nUnsupportedOperationException<\/code> indicating that it is not supported in the list.<\/p>\nsingletonList<\/code> method is generic meaning that it can handle any data type<\/a> and, in our case just pass the HashMap reference and it will automatically infer the type.<\/p>\n\npublic static void main(String[] arg){\n HashMapPrint HashMap using getkey() and getValue with entrySet()<\/span><\/h2>\n
getKey()<\/code> and getValue()<\/code> methods, we use the entrySet()<\/code> method which returns a Set of Map entries Map.Entry<\/code>.<\/p>\nSet<\/code> is a Collection the only way to reference the Map entry is by using an iterator inherited from the Iterable<\/code> class.<\/p>\n\npublic static void main(String[] arg){\n HashMap
\n2 = mansion
\n3 = flat\n<\/div>\nPrint HashMap using BiConsumer<\/span><\/h2>\n
forEach()<\/code> method. The for-each method is inherited by the HashMap from the Map<\/code> interface.<\/p>\nBiConsumer<\/code>.<\/p>\naccept()<\/code> method behind the scenes to receive the key and value parameters from the HashMap.<\/p>\nCurrentModificationException<\/code>, respectively.<\/p>\n\npublic static void main(String[] arg){\n HashMap
\njohn doe
\ndonald trump
\npeter parker\n<\/div>\nPrint HashMap using Iterator<\/span><\/h2>\n
iterator()<\/code> method through the entrySet()<\/code> method, which returns a Set containing Map entries.<\/p>\nforEachRemaining()<\/code> method to iterate through the elements.<\/p>\nforEachRemaining<\/code> is a method from the Iterator interface that we will use to print out the elements in the HashMap by passing a Consumer.<\/p>\n\npublic static void main(String[] arg){\n HashMap