Exploring the map() function in Java Streams API

15 Sep 2023

In Java, the Streams API provides powerful functionality for processing and manipulating collections of data. One of the key functions in the Streams API is the map() function. The map() function allows you to transform each element in a stream to another element, based on a provided mapping function. This can be extremely useful when you want to apply some logic or modify the data in a collection.

Syntax

The syntax for the map() function is as follows:

stream.map(mappingFunction)

Where stream is the stream of elements and mappingFunction is a function that takes an element from the input stream, performs some transformation on it, and returns the transformed element.

Example

Let’s consider an example where we have a list of strings representing names, and we want to convert each name to uppercase using the map() function:

List<String> names = Arrays.asList("John", "Jane", "Mike", "Emily");

List<String> upperCaseNames = names.stream()
                                   .map(String::toUpperCase)
                                   .collect(Collectors.toList());

System.out.println(upperCaseNames);

In this example, we create a stream from the names list using the stream() method. We then apply the map() function to transform each name to uppercase using the method reference String::toUpperCase. Finally, we collect the transformed elements into a new list using the collect() method with Collectors.toList().

The output of the code will be:

[JOHN, JANE, MIKE, EMILY]

Conclusion

The map() function in Java Streams API is a powerful tool for transforming elements in a stream. By using map(), you can easily modify and manipulate data in collections. It provides a clean and concise way to apply logic to each element in the stream. Incorporating the map() function in your code can greatly simplify your data processing tasks.

Syntax

Example

Conclusion

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