solutions to exercise problems

src/main/java/io/javabrains/reactiveworkshop/Exercise1.java

@@ -1,30 +1,46 @@
 package io.javabrains.reactiveworkshop;
 
-public class Exercise1 {
-
-    public static void main(String[] args) {
-
-        // Use StreamSources.intNumbersStream() and StreamSources.userStream()
-
-        // Print all numbers in the intNumbersStream stream
-        // TODO: Write code here
-
-        // Print numbers from intNumbersStream that are less than 5
-        // TODO: Write code here
+import java.util.List;
 
-        // Print the second and third numbers in intNumbersStream that's greater than 5
-        // TODO: Write code here
-
-        //  Print the first number in intNumbersStream that's greater than 5.
-        //  If nothing is found, print -1
-        // TODO: Write code here
-
-        // Print first names of all users in userStream
-        // TODO: Write code here
-
-        // Print first names in userStream for users that have IDs from number stream
-        // TODO: Write code here
-
-    }
+public class Exercise1 {
 
+  public static void main(String[] args) {
+
+    // Use StreamSources.intNumbersStream() and StreamSources.userStream()
+
+    // Print all numbers in the intNumbersStream stream
+    StreamSources.intNumbersStream().forEach(System.out::println);
+
+    // Print numbers from intNumbersStream that are less than 5
+    StreamSources.intNumbersStream().filter(number -> number < 5).forEach(System.out::println);
+
+    // Print the second and third numbers in intNumbersStream that's greater than 5
+    StreamSources.intNumbersStream()
+        .filter(number -> number > 5)
+        .skip(1L)
+        .limit(2)
+        .forEach(System.out::println);
+
+    //  Print the first number in intNumbersStream that's greater than 5.
+    //  If nothing is found, print -1
+    Integer integer =
+        StreamSources.intNumbersStream().filter(number -> number > 5).findFirst().orElse(-1);
+    System.out.println(integer);
+
+    // Print first names of all users in userStream
+    StreamSources.userStream().map(User::getFirstName).forEach(System.out::println);
+
+    // Print first names in userStream for users that have IDs from number stream
+    //    Solution-1
+    StreamSources.intNumbersStream()
+        .flatMap(userId -> StreamSources.userStream().filter(user -> user.getId() == userId))
+        .map(User::getFirstName)
+        .forEachOrdered(System.out::println);
+    //   Solution-2
+    List<Integer> userIds = StreamSources.intNumbersStream().toList();
+    StreamSources.userStream()
+        .filter(user -> userIds.contains(user.getId()))
+        .map(User::getFirstName)
+        .forEach(System.out::println);
+  }
 }

src/main/java/io/javabrains/reactiveworkshop/Exercise2.java

@@ -1,21 +1,24 @@
 package io.javabrains.reactiveworkshop;
 
+import reactor.core.publisher.Flux;
+
 import java.io.IOException;
 
 public class Exercise2 {
 
-    public static void main(String[] args) throws IOException {
-
-        // Use ReactiveSources.intNumbersFlux() and ReactiveSources.userFlux()
+  public static void main(String[] args) throws IOException {
 
-        // Print all numbers in the ReactiveSources.intNumbersFlux stream
-        // TODO: Write code here
+    // Use ReactiveSources.intNumbersFlux() and ReactiveSources.userFlux()
+    Flux<Integer> intNumbersFlux = ReactiveSources.intNumbersFlux();
+    Flux<User> userFlux = ReactiveSources.userFlux();
 
-        // Print all users in the ReactiveSources.userFlux stream
-        // TODO: Write code here
+    // Print all numbers in the ReactiveSources.intNumbersFlux stream
+    intNumbersFlux.subscribe(System.out::println);
 
-        System.out.println("Press a key to end");
-        System.in.read();
-    }
+    // Print all users in the ReactiveSources.userFlux stream
+    userFlux.subscribe(System.out::println);
 
+    System.out.println("Press a key to end");
+    System.in.read();
+  }
 }

src/main/java/io/javabrains/reactiveworkshop/Exercise3.java

@@ -1,20 +1,26 @@
 package io.javabrains.reactiveworkshop;
 
+import reactor.core.publisher.Flux;
+
 import java.io.IOException;
+import java.util.List;
+import java.util.stream.Collectors;
 
 public class Exercise3 {
 
-    public static void main(String[] args) throws IOException {
-
-        // Use ReactiveSources.intNumbersFlux()
+  public static void main(String[] args) throws IOException {
 
-        // Get all numbers in the ReactiveSources.intNumbersFlux stream
-        // into a List and print the list and its size
-        // TODO: Write code here
+    // Use ReactiveSources.intNumbersFlux()
+    Flux<Integer> intNumbersFlux = ReactiveSources.intNumbersFlux();
 
+    // Get all numbers in the ReactiveSources.intNumbersFlux stream
+    // into a List and print the list and its size
+    List<Integer> numbers = intNumbersFlux.toStream().collect(Collectors.toList());
 
-        System.out.println("Press a key to end");
-        System.in.read();
-    }
+    System.out.println(numbers);
+    System.out.println("Size: " + numbers.size());
 
+    System.out.println("Press a key to end");
+    System.in.read();
+  }
 }

src/main/java/io/javabrains/reactiveworkshop/Exercise4.java

@@ -1,21 +1,24 @@
 package io.javabrains.reactiveworkshop;
 
+import reactor.core.publisher.Mono;
+
 import java.io.IOException;
 
 public class Exercise4 {
 
-    public static void main(String[] args) throws IOException {
-
-        // Use ReactiveSources.intNumberMono()
+  public static void main(String[] args) throws IOException {
 
-        // Print the value from intNumberMono when it emits
-        // TODO: Write code here
+    // Use ReactiveSources.intNumberMono()
+    Mono<Integer> intNumberMono = ReactiveSources.intNumberMono();
 
-        // Get the value from the Mono into an integer variable
-        // TODO: Write code here
+    // Print the value from intNumberMono when it emits
+    intNumberMono.subscribe(System.out::println);
 
-        System.out.println("Press a key to end");
-        System.in.read();
-    }
+    // Get the value from the Mono into an integer variable
+    Integer integer = intNumberMono.block();
+    System.out.println("Integer value: " + integer);
 
+    System.out.println("Press a key to end");
+    System.in.read();
+  }
 }

src/main/java/io/javabrains/reactiveworkshop/Exercise5.java

@@ -1,21 +1,45 @@
 package io.javabrains.reactiveworkshop;
 
+import reactor.core.publisher.BaseSubscriber;
+
 import java.io.IOException;
 
 public class Exercise5 {
 
-    public static void main(String[] args) throws IOException {
+  public static void main(String[] args) throws IOException {
+
+    // Use ReactiveSources.intNumberMono() and ReactiveSources.userMono()
+
+    // Subscribe to a flux using the error and completion hooks
+    ReactiveSources.intNumbersFlux()
+        .subscribe(
+            System.out::println,
+            Throwable::printStackTrace,
+            () -> System.out.println("Complete signal"));
+
+    // Subscribe to a flux using an implementation of BaseSubscriber
+    BaseSubscriber<Integer> baseSubscriber =
+        new BaseSubscriber<>() {
 
-        // Use ReactiveSources.intNumberMono() and ReactiveSources.userMono()
+          @Override
+          protected void hookOnNext(Integer value) {
+            System.out.println(value);
+          }
 
-        // Subscribe to a flux using the error and completion hooks
-        // TODO: Write code here
+          @Override
+          protected void hookOnError(Throwable throwable) {
+            System.out.println("Exception occurred: " + throwable);
+          }
 
-        // Subscribe to a flux using an implementation of BaseSubscriber
-        // TODO: Write code here
+          @Override
+          protected void hookOnComplete() {
+            System.out.println("Complete signal");
+          }
+        };
 
-        System.out.println("Press a key to end");
-        System.in.read();
-    }
+    ReactiveSources.intNumbersFlux().subscribe(baseSubscriber);
 
-}
+    System.out.println("Press a key to end");
+    System.in.read();
+  }
+}

src/main/java/io/javabrains/reactiveworkshop/Exercise6.java

@@ -1,23 +1,47 @@
 package io.javabrains.reactiveworkshop;
 
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
 import java.io.IOException;
+import java.time.Duration;
+import java.util.List;
 
 public class Exercise6 {
 
-
-    public static void main(String[] args) throws IOException {
-
-        // Use ReactiveSources.unresponsiveFlux() and ReactiveSources.unresponsiveMono()
-
-        // Get the value from the Mono into a String variable but give up after 5 seconds
-        // TODO: Write code here
-
-        // Get the value from unresponsiveFlux into a String list but give up after 5 seconds
-        // Come back and do this when you've learnt about operators!
-        // TODO: Write code here
-
-        System.out.println("Press a key to end");
-        System.in.read();
-    }
-
+  public static void main(String[] args) throws IOException {
+
+    // Use ReactiveSources.unresponsiveFlux() and ReactiveSources.unresponsiveMono()
+    Flux<String> unresponsiveFlux = ReactiveSources.unresponsiveFlux();
+    Mono<String> unresponsiveMono = ReactiveSources.unresponsiveMono();
+
+    // Get the value from the Mono into a String variable but give up after 5 seconds
+    String valueFromMono =
+        unresponsiveMono
+            .timeout(Duration.ofSeconds(5L))
+            .doOnError(
+                e ->
+                    System.out.println(
+                        "Could not retrieve the value from unresponsiveMono within 5 seconds"))
+            .onErrorReturn("")
+            .block();
+    System.out.println(valueFromMono);
+
+    // Get the value from unresponsiveFlux into a String list but give up after 5 seconds
+    List<String> valueFromFlux =
+        unresponsiveFlux
+            .timeout(Duration.ofSeconds(5L))
+            .doOnError(
+                e ->
+                    System.out.println(
+                        "Could not retrieve the value from unresponsiveFlux within 5 seconds"))
+            .onErrorReturn("")
+            .collectList()
+            .block();
+
+    System.out.println(valueFromFlux);
+
+    System.out.println("Press a key to end");
+    System.in.read();
+  }
 }

src/main/java/io/javabrains/reactiveworkshop/Exercise7.java

@@ -1,37 +1,51 @@
 package io.javabrains.reactiveworkshop;
 
+import reactor.core.publisher.Flux;
+
 import java.io.IOException;
 
 public class Exercise7 {
 
+  public static void main(String[] args) throws IOException {
 
-    public static void main(String[] args) throws IOException {
-
-        // Use ReactiveSources.intNumberMono() and ReactiveSources.userMono()
-
-        // Print all values from intNumbersFlux that's greater than 5
-        // TODO: Write code here
+    // Use ReactiveSources.intNumberMono() and ReactiveSources.userMono()
 
-        // Print 10 times each value from intNumbersFlux that's greater than 5
-        // TODO: Write code here
+    Flux<Integer> intNumbersFlux = ReactiveSources.intNumbersFlux();
+    Flux<User> userFLux = ReactiveSources.userFlux();
+    Flux<Integer> intNumbersFluxWithRepeat = ReactiveSources.intNumbersFluxWithRepeat();
 
-        // Print 10 times each value from intNumbersFlux for the first 3 numbers emitted that's greater than 5
-        // TODO: Write code here
+    // Print all values from intNumbersFlux that's greater than 5
+    intNumbersFlux.filter(number -> number > 5).subscribe(System.out::println);
 
-        // Print each value from intNumbersFlux that's greater than 20. Print -1 if no elements are found
-        // TODO: Write code here
+    // Print 10 times each value from intNumbersFlux that's greater than 5
+    intNumbersFlux
+        .filter(number -> number > 5)
+        .map(number -> number * 10)
+        .subscribe(System.out::println);
 
-        // Switch ints from intNumbersFlux to the right user from userFlux
-        // TODO: Write code here
+    // Print 10 times each value from intNumbersFlux for the first 3 numbers emitted that's greater
+    // than 5
+    intNumbersFlux
+        .filter(number -> number > 5)
+        .take(3)
+        .map(number -> number * 10)
+        .subscribe(System.out::println);
+    // Print each value from intNumbersFlux that's greater than 20. Print -1 if no elements are
+    // found
+    intNumbersFlux.filter(number -> number > 20).or(Flux.just(-1)).subscribe(System.out::println);
 
-        // Print only distinct numbers from intNumbersFluxWithRepeat
-        // TODO: Write code here
+    // Switch ints from intNumbersFlux to the right user from userFlux
+    intNumbersFlux
+        .flatMap(userId -> userFLux.filter(user -> user.getId() == userId))
+        .subscribe(System.out::println);
 
-        // Print from intNumbersFluxWithRepeat excluding immediately repeating numbers
-        // TODO: Write code here
+    // Print only distinct numbers from intNumbersFluxWithRepeat
+    intNumbersFluxWithRepeat.distinct().subscribe(System.out::println);
 
-        System.out.println("Press a key to end");
-        System.in.read();
-    }
+    // Print from intNumbersFluxWithRepeat excluding immediately repeating numbers
+    intNumbersFluxWithRepeat.distinctUntilChanged().subscribe(System.out::println);
 
+    System.out.println("Press a key to end");
+    System.in.read();
+  }
 }