Creates a few examples of how to use Streams with Map from Java 8

Author: alexandregama

java8-stream-map/src/test/java/com/craftcoder/java8/stream/map/StreamWithMapTest.java

@@ -1,5 +1,65 @@
 package com.craftcoder.java8.stream.map;
 
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.contains;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+import org.junit.Test;
+
 public class StreamWithMapTest {
+
+	@Test
+	public void shouldMultiplyEachElementBy2() throws Exception {
+		List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);
+		
+		Function<Integer, Integer> multiplyBy2 = new Function<Integer, Integer>() {
+
+			@Override
+			public Integer apply(Integer number) {
+				return number * 2;
+			}
+		};
+		
+		List<Integer> multipliedNumbers = numbers
+			.stream()
+			.map(multiplyBy2)
+			.collect(Collectors.toList());
+		
+		assertThat(multipliedNumbers, contains(2, 4, 6, 8, 10));
+	}
+	
+	@Test
+	public void shouldMultiplyEachElementBy2UsingLambdaExpression() throws Exception {
+		List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);
+		
+		Function<Integer, Integer> multiplyBy2 = number -> number * 2; 
+		
+		List<Integer> multipliedNumbers = numbers
+				.stream()
+				.map(multiplyBy2)
+				.collect(Collectors.toList());
+		
+		assertThat(multipliedNumbers, contains(2, 4, 6, 8, 10));
+	}
+	
+	@Test
+	public void shouldMultiplyAndTransformIntoStringEachElement() throws Exception {
+		List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);
+		
+		Function<Integer, Integer> multiplyBy2 = number -> number * 2; 
+		Function<Integer, String> transformIntoString = number -> String.valueOf(number); 
+		
+		List<String> multipliedNumbersAsString = numbers
+				.stream()
+				.map(multiplyBy2)
+				.map(transformIntoString)
+				.collect(Collectors.toList());
+		
+		assertThat(multipliedNumbersAsString, contains("2", "4", "6", "8", "10"));
+	}
 
 }