[BAEL 5909]-Callable vs Supplier and When to Use Them in Java (#13041)

* Added test class for a simple shallow copy and deep copy

* Added test class for a simple shallow copy and deep copy

* refactor naming of test method

* formatted

* refactor test whenIsAShallowCopyDoneByCopyConstructor_thenImmutableObjectWillNotChange

* Renamed package and added md file

* refactor README.md

* first push

* refactor

* Revert "refactor README.md"

This reverts commit eae77c453ba0bf2af62bad52dc1ed61d07931e34.

* Revert "Renamed package and added md file"

This reverts commit 42c6f97cbde39cc0a5e0bacf34f86a32ded4f4aa.

* Revert "refactor test whenIsAShallowCopyDoneByCopyConstructor_thenImmutableObjectWillNotChange"

This reverts commit 44fb57fe2b51857f960dc216d33508e718e5414f.

* Revert "formatted"

This reverts commit 44be87ef25e566b8e9175cb0fdeed7f0ef485dd3.

* Revert "refactor naming of test method"

This reverts commit 6133c31057e39b19c4978f960cda1c0ba5559aae.

* Revert "Added test class for a simple shallow copy and deep copy"

This reverts commit 2cae083578883ae693d1c5e76fd4948e213e9ea0.

* Revert "Added test class for a simple shallow copy and deep copy"

This reverts commit f43312e2c1979410409f46020a3f7d555e11e966.

* Merge prohect java-supplier-callable to project core-java-lambdas

* adjusted package name

* removed AbstractAgeCalculator.java

* added test for supplier-callable

Co-authored-by: Cesare <cesare.valenti@hotmail.com>

core-java-modules/core-java-lambdas/src/main/java/com/baeldung/suppliercallable/data/User.java

@@ -0,0 +1,59 @@
+package com.baeldung.suppliercallable.data;
+
+import java.time.LocalDate;
+
+public class User {
+
+    private String name;
+    private String surname;
+    private LocalDate birthDate;
+    private Integer age;
+    private Boolean canDriveACar = false;
+
+    public User(String name, String surname, LocalDate birthDate) {
+        this.name = name;
+        this.surname = surname;
+        this.birthDate = birthDate;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getSurname() {
+        return surname;
+    }
+
+    public void setSurname(String surname) {
+        this.surname = surname;
+    }
+
+    public LocalDate getBirthDate() {
+        return birthDate;
+    }
+
+    public void setBirthDate(LocalDate birthDate) {
+        this.birthDate = birthDate;
+    }
+
+    public void setAge(Integer age) {
+        this.age = age;
+    }
+
+    public Integer getAge() {
+        return age;
+    }
+
+    public Boolean getCanDriveACar() {
+        return canDriveACar;
+    }
+
+    public void setCanDriveACar(Boolean canDriveACar) {
+        this.canDriveACar = canDriveACar;
+    }
+
+}

core-java-modules/core-java-lambdas/src/main/java/com/baeldung/suppliercallable/service/Service.java

@@ -0,0 +1,8 @@
+package com.baeldung.suppliercallable.service;
+
+import com.baeldung.suppliercallable.data.User;
+
+public interface Service {
+
+    User execute(User user);
+}

core-java-modules/core-java-lambdas/src/main/java/com/baeldung/suppliercallable/service/callable/AgeCalculatorCallable.java

@@ -0,0 +1,20 @@
+package com.baeldung.suppliercallable.service.callable;
+
+import java.time.LocalDate;
+import java.time.Period;
+import java.util.concurrent.Callable;
+
+public class AgeCalculatorCallable implements Callable<Integer> {
+
+    private final LocalDate birthDate;
+
+    @Override
+    public Integer call() throws Exception {
+        return Period.between(birthDate, LocalDate.now())
+          .getYears();
+    }
+
+    public AgeCalculatorCallable(LocalDate birthDate) {
+        this.birthDate = birthDate;
+    }
+}

core-java-modules/core-java-lambdas/src/main/java/com/baeldung/suppliercallable/service/callable/CallableServiceImpl.java

@@ -0,0 +1,31 @@
+package com.baeldung.suppliercallable.service.callable;
+
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+import com.baeldung.suppliercallable.data.User;
+import com.baeldung.suppliercallable.service.Service;
+
+public class CallableServiceImpl implements Service {
+
+    @Override
+    public User execute(User user) {
+        ExecutorService executorService = Executors.newCachedThreadPool();
+
+        try {
+            Future<Integer> ageFuture = executorService.submit(new AgeCalculatorCallable(user.getBirthDate()));
+            Integer age = ageFuture.get();
+            Future<Boolean> canDriveACarFuture = executorService.submit(new CarDriverValidatorCallable(age));
+            Boolean canDriveACar = canDriveACarFuture.get();
+            user.setAge(age);
+            user.setCanDriveACar(canDriveACar);
+        } catch (ExecutionException | InterruptedException e) {
+            throw new RuntimeException(e.getCause());
+        }
+
+        return user;
+    }
+
+}

core-java-modules/core-java-lambdas/src/main/java/com/baeldung/suppliercallable/service/callable/CarDriverValidatorCallable.java

@@ -0,0 +1,17 @@
+package com.baeldung.suppliercallable.service.callable;
+
+import java.util.concurrent.Callable;
+
+public class CarDriverValidatorCallable implements Callable<Boolean> {
+
+    private final Integer age;
+
+    @Override
+    public Boolean call() throws Exception {
+        return age > 18;
+    }
+
+    public CarDriverValidatorCallable(Integer age) {
+        this.age = age;
+    }
+}

core-java-modules/core-java-lambdas/src/main/java/com/baeldung/suppliercallable/service/supplier/SupplierServiceImpl.java

@@ -0,0 +1,26 @@
+package com.baeldung.suppliercallable.service.supplier;
+
+import java.time.LocalDate;
+import java.time.Period;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import com.baeldung.suppliercallable.data.User;
+import com.baeldung.suppliercallable.service.Service;
+
+public class SupplierServiceImpl implements Service {
+    @Override
+    public User execute(User user) {
+        ExecutorService executorService = Executors.newCachedThreadPool();
+        CompletableFuture<Integer> ageFut = CompletableFuture.supplyAsync(() -> Period.between(user.getBirthDate(), LocalDate.now())
+          .getYears(), executorService)
+          .exceptionally((throwable -> null));
+        CompletableFuture<Boolean> canDriveACarFut = ageFut.thenComposeAsync(age -> CompletableFuture.supplyAsync(() -> age > 18, executorService))
+          .exceptionally((ex) -> false);
+        user.setAge(ageFut.join());
+        user.setCanDriveACar(canDriveACarFut.join());
+        return user;
+    }
+
+}

core-java-modules/core-java-lambdas/src/test/java/com/baeldung/suppliercallable/CallableSupplierUnitTest.java

@@ -0,0 +1,64 @@
+package com.baeldung.suppliercallable;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import java.time.LocalDate;
+import java.time.Month;
+import org.junit.jupiter.api.Test;
+import com.baeldung.suppliercallable.data.User;
+import com.baeldung.suppliercallable.service.Service;
+import com.baeldung.suppliercallable.service.callable.CallableServiceImpl;
+import com.baeldung.suppliercallable.service.supplier.SupplierServiceImpl;
+
+public class CallableSupplierUnitTest {
+
+    @Test
+    void givenCallableService_whenUserIsAnAdult_thenCanDriveACar() {
+        User user = new User("Test", "Test", LocalDate.of(2000, Month.JANUARY, 19));
+        Service service = new CallableServiceImpl();
+        service.execute(user);
+        assertEquals(true, user.getCanDriveACar());
+    }
+
+    @Test
+    void givenCallableService_whenUserIsNotAnAdult_thenCannotDriveACar() {
+        User user = new User("Test", "Test", LocalDate.of(2010, Month.JANUARY, 19));
+        Service service = new CallableServiceImpl();
+        service.execute(user);
+        assertEquals(false, user.getCanDriveACar());
+    }
+
+    @Test
+    void givenCallableService_whenBirthDateIsNull_thenShouldThrowAnException() {
+        User user = new User("Test", "Test", null);
+        Service service = new CallableServiceImpl();
+        assertThrows(RuntimeException.class, () -> service.execute(user));
+    }
+
+    @Test
+    void givenSupplierService_whenUserIsAnAdult_thenCanDriveACar() {
+        User user = new User("Test", "Test", LocalDate.of(2000, Month.JANUARY, 19));
+        Service service = new SupplierServiceImpl();
+        service.execute(user);
+        assertEquals(true, user.getCanDriveACar());
+    }
+
+    @Test
+    void givenSupplierService_whenUserIsNotAnAdult_thenCannotDriveACar() {
+        User user = new User("Test", "Test", LocalDate.of(2010, Month.JANUARY, 19));
+        Service service = new SupplierServiceImpl();
+        service.execute(user);
+        assertEquals(false, user.getCanDriveACar());
+    }
+
+    @Test
+    void givenSupplierService_whenBirthDateIsNull_thenCannotDriveACarAndAgeIsNull() {
+        User user = new User("Test", "Test", null);
+        Service service = new SupplierServiceImpl();
+        service.execute(user);
+        assertEquals(false, user.getCanDriveACar());
+        assertNull(user.getBirthDate());
+    }
+
+}