BAEL-2074: Lombok builder with custom setter

lombok/README.md

@@ -4,3 +4,4 @@
 - [Using Lombok’s @Getter for Boolean Fields](https://www.baeldung.com/lombok-getter-boolean)
 - [Lombok @Builder with Inheritance](https://www.baeldung.com/lombok-builder-inheritance)
 - [Lombok Builder with Default Value](https://www.baeldung.com/lombok-builder-default-value)
+- [Lombok Builder with Custom Setter](https://www.baeldung.com/lombok-builder-with-custom-setter)

lombok/src/main/java/com/baeldung/lombok/builder/customsetter/Message.java

@@ -0,0 +1,39 @@
+package com.baeldung.lombok.builder.customsetter;
+
+import java.io.File;
+import java.util.List;
+
+import lombok.Builder;
+import lombok.Data;
+
+@Builder
+@Data
+public class Message {
+    private String sender;
+    private String recipient;
+    private String text;
+    private File file;
+
+    public static class MessageBuilder {
+        private String text;
+        private File file;
+
+        public MessageBuilder text(String text) {
+            this.text = text;
+            verifyTextOrFile();
+            return this;
+        }
+
+        public MessageBuilder file(File file) {
+            this.file = file;
+            verifyTextOrFile();
+            return this;
+        }
+
+        private void verifyTextOrFile() {
+            if (text != null && file != null) {
+                throw new IllegalArgumentException("Cannot send 'text' and 'file'.");
+            }
+        }
+    }
+}

lombok/src/test/java/com/baeldung/lombok/builder/customsetter/BuilderWithCustomSetterUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.lombok.builder.customsetter;
+
+import java.io.File;
+
+import org.junit.Test;
+
+public class BuilderWithCustomSetterUnitTest {
+
+    @Test
+    public void givenBuilderWithCustomSetter_TestTextOnly() {
+        Message message = Message.builder()
+            .sender("user@somedomain.com")
+            .recipient("someuser@otherdomain.com")
+            .text("How are you today?")
+            .build();
+    }
+
+    @Test
+    public void givenBuilderWithCustomSetter_TestFileOnly() {
+        Message message = Message.builder()
+            .sender("user@somedomain.com")
+            .recipient("someuser@otherdomain.com")
+            .file(new File("/path/to/file"))
+            .build();
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void givenBuilderWithCustomSetter_TestTextAndFile() {
+        Message message = Message.builder()
+            .sender("user@somedomain.com")
+            .recipient("someuser@otherdomain.com")
+            .text("How are you today?")
+            .file(new File("/path/to/file"))
+            .build();
+    }
+
+}