JAVA EE: How to use map method of stream to convert all string elements in an array to uppercase

Tuesday 25 July 2017

How to use map method of stream to convert all string elements in an array to uppercase

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https://www.youtube.com/watch?v=jl61UnWSkQQ&list=UUhwKlOVR041tngjerWxVccw

StreamDemo.java

import java.util.Arrays;
import java.util.stream.Stream;

/**
 * Once you have a Stream object, you can use a variety of methods to
 * transform it into another Stream object. The first such method
 * we’re going to look at is the map method. It takes a lambda
 * expression as its only argument, and uses it to change every
 * individual element in the stream. Its return value is a new Stream
 * object containing the changed elements.
 *
 * How to use map to convert all elements in an array of strings to
 * uppercase.
 */
public class StreamDemo
{
    public static void main(String[] args)
    {
        String[] nameArray = new String[] { "Peter", "Steve", "paul", "Ram" };

        Stream<String> stream = Arrays.stream(nameArray);

        /*
         * passing a lambda expression, one which can convert a string
         * to uppercase.
         *
         * The Stream object returned contains the changed strings.
         */
        Stream<String> upperCaseStream = stream.map(name -> name.toUpperCase());

        String[] upperCaseNameArray = upperCaseStream.toArray(String[]::new);

        for (String name : upperCaseNameArray)
        {
            System.out.println(name);
        }

    }
}