BAEL-1787 - Use Lombok @Builder Annotation (#4302)

* BAEL-1787 - using Lombok @Builder on methods

* BAEL-1787 - rename class. Add AssertJ to Lombok project.

* BAEL-1787 - rename class again. Change AssertJ tests.

* BAEL-1787 - add Builder directory. Move method cocde to that package. Add code for using builder with a class.

lombok/src/main/java/com/baeldung/lombok/builder/ClientBuilder.java

@@ -0,0 +1,11 @@
+package com.baeldung.lombok.builder;
+
+import lombok.Builder;
+
+class ClientBuilder {
+
+    @Builder(builderMethodName = "builder")
+    public static ImmutableClient newClient(int id, String name) {
+        return new ImmutableClient(id, name);
+    }
+}

lombok/src/main/java/com/baeldung/lombok/builder/ImmutableClient.java

@@ -0,0 +1,11 @@
+package com.baeldung.lombok.builder;
+
+import lombok.Value;
+
+@Value
+final class ImmutableClient {
+
+    private int id;
+    private String name;
+
+}

lombok/src/main/java/com/baeldung/lombok/builder/Widget.java

@@ -0,0 +1,13 @@
+package com.baeldung.lombok.builder;
+
+import lombok.Builder;
+import lombok.Getter;
+
+@Getter
+@Builder(toBuilder = true)
+public class Widget {
+
+    private final String name;
+    private final int id;
+
+}

lombok/src/test/java/com/baeldung/lombok/builder/BuilderUnitTest.java

@@ -0,0 +1,42 @@
+package com.baeldung.lombok.builder;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.*;
+
+public class BuilderUnitTest
+{
+
+    @Test
+    public void givenBuilder_WidgetIsBuilt() {
+        Widget testWidget = Widget.builder().name("foo").id(1).build();
+        assertThat(testWidget.getName())
+                .isEqualTo("foo");
+        assertThat(testWidget.getId())
+                .isEqualTo(1);
+    }
+
+    @Test
+    public void givenToBuilder_whenToBuilder_BuilderIsCreated() {
+
+        Widget testWidget = Widget.builder().name("foo").id(1).build();
+        Widget.WidgetBuilder widgetBuilder = testWidget.toBuilder();
+
+        Widget newWidget = widgetBuilder.id(2).build();
+        assertThat(newWidget.getName())
+                .isEqualTo("foo");
+        assertThat(newWidget.getId())
+                .isEqualTo(2);
+    }
+
+
+
+    @Test
+    public void givenBuilderMethod_ClientIsBuilt() {
+        ImmutableClient testImmutableClient = ClientBuilder.builder().name("foo").id(1).build();
+        assertThat(testImmutableClient.getName())
+            .isEqualTo("foo");
+        assertThat(testImmutableClient.getId())
+            .isEqualTo(1);
+    }
+}