Add classes for stream operations: ConcatTwoStreams, FlatMapExample, Person, and SumProductMaxUsingStreams

Author: kumarcodes

src/main/java/com/java8/ConcatTwoStreams.java

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+package com.java8;
+
+import java.util.stream.Stream;
+
+public class ConcatTwoStreams {
+    public static void main(String[] args) {
+        Stream<String> stream1 = Stream.of("Java", "Python");
+        Stream<String> stream2 = Stream.of("C", ".NET");
+        Stream<String> concatStream = Stream.concat(stream1, stream2);
+        concatStream.forEach(System.out::println);
+
+    }
+}

src/main/java/com/java8/FlatMapExample.java

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+package com.java8;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class FlatMapExample {
+    public static void main(String[] args) {
+        List<Person> personList = Arrays.asList(new Person("Alice", Arrays.asList("Red", "Yellow")),
+                new Person("Tom", Arrays.asList("Blue", "Orange", "Red")),
+                new Person("Bob", Arrays.asList("Red", "Yellow", "Black")));
+        List<List<String>> colorList = personList.stream().map(Person::getColor).toList();
+        System.out.println(colorList);
+        List<String> colors = personList.stream().flatMap(x->x.getColor().stream()).toList();
+        System.out.println(colors);
+    }
+}

src/main/java/com/java8/Person.java

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+package com.java8;
+
+import java.util.List;
+
+public class Person {
+    String name;
+    List<String> color;
+
+    public Person(String name, List<String> color) {
+        this.name = name;
+        this.color = color;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public List<String> getColor() {
+        return color;
+    }
+
+    public void setColor(List<String> color) {
+        this.color = color;
+    }
+}

src/main/java/com/java8/SumProductMaxUsingStreams.java

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+package com.java8;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
+
+public class SumProductMaxUsingStreams {
+    public static void main(String[] args) {
+        List<Integer> integerList = Arrays.asList(1, 2, 3, 4, 5);
+        Optional<Integer> sum = integerList.stream().reduce((a, b) -> a + b);
+        System.out.println("Sum of given list of integers: " + sum.orElse(1));
+        Optional<Integer> max = integerList.stream().reduce(Integer::max);
+        System.out.println("Maximum of given list of integers: " + max.orElse(-1));
+        Optional<Integer> product = integerList.stream().reduce((a, b) -> a * b);
+        System.out.println("Product of given list of integers: " + product.orElse(1));
+    }
+}