![]() ![]() The output will be: The Transformed list : In the above code snippet, Stream is an input stream for map().Ĭountry::getName is the mapper function that is applied to each Country and the outcome is collected in a List called namesOfCountries. ("The Transformed list : " + namesOfCountries) List namesOfCountries = countryList.stream()ĥ. Now, you can extract name of each Country, using the map() method as shown below: 1. countryList.add(new Country("India", Arrays.asList("Delhi", "Mumbai", "Lucknow", "Bangalore"))) countryList.add(new Country("Pakistan", Arrays.asList("Karachi", "Islamabad", "Lahore", “Multan” ))) ĩ. countryList.add(new Country("USA", Arrays.asList("New York", "Chicago", "Washington D.C.", "Miami"))) Ĩ. One is the name of the country and another one is its some notable cities wrapped in another List as shown below: 1. Suppose we have a country List where each Country consists of two fields. See this another example where Map() is used to extract data from a list. s -> s.length() is the mapper function that is applied to each Country and the result is collected in a List called list. In the code demonstrated above, Stream is an input stream for map(). The Map() method is then used to transform the list into the length of the name of each country added to the array list. ("Transformed list : " + list) įollowing is the output: List of Countries : įirst, an array list object is created where names of some countries are added to the array list. Now map() is used to transform the list of countriesĢ4. See the following code demonstration using the map() to transform a list: 1. The map() function can be used where it is required to map the elements of a particular collection to a certain function, and the new stream containing the updated results is to be returned.įor instance, the map() can be used to Multiply all the elements of the list by 5 and then return the results in the updated list. The given mapper function is applied to each element of input Stream and results are then stored in an output Stream. The mapper is a stateless function that is applied to each element.The T represents the type of stream elements.Here, the R is the element type of the new output stream.The Syntax of the map() method is as follows: Stream map(Function mapper) ![]() The Java map() method takes one input value and produced one output hence, it is also referred to as One-To-One mapping. In this article, we will further explore the map() and flatmap() methods, the key differences between them and will discover the correct and most suitable use of both of them with the aid of relevant examples. The map() offers transformation whereas the flatmap() can be used for both transformations and flattening, thus the name flatmap. The Java flatmap() and map() methods were first just used in functional languages but they were soon introduced in Java 8. They both are methods of interface in Java 8 that is primarily used for transformation or mapping operations. The map() and flatmap() are two very significant operations in Java. ![]()
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