Initial commit: Task 6 completed - Sealed class PaymentException with pattern matching

.gitignore

+### IntelliJ IDEA ###
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store
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.idea/.gitignore

+# Default ignored files
+/shelf/
+/workspace.xml

.idea/misc.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_17" default="true" project-jdk-name="ms-17" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/out" />
+  </component>
+</project>
\ No newline at end of file

.idea/modules.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/untitled.iml" filepath="$PROJECT_DIR$/untitled.iml" />
+    </modules>
+  </component>
+</project>
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.idea/vcs.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$/.." vcs="Git" />
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+  </component>
+</project>
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src/InvalidOfferAppliedException.java

+public final class InvalidOfferAppliedException extends PaymentException {
+    public InvalidOfferAppliedException(String message) {
+        super(message);
+    }
+}

src/InvalidPaymentMethodException.java

+public final class InvalidPaymentMethodException extends PaymentException {
+        public InvalidPaymentMethodException(String message) {
+            super(message);
+        }
+    }
+

src/Main.java

+public class Main {
+    public static void processPaymentMethod(String method, String offer) {
+        PaymentService paymentService = new PaymentService();
+
+        try {
+            paymentService.paymentMethod(method, offer);
+        } catch (PaymentException e) {
+            if (e instanceof InvalidPaymentMethodException ipm) {
+                System.out.println("Payment failed: " + ipm.getMessage());
+            } else if (e instanceof InvalidOfferAppliedException ioa) {
+                System.out.println("Offer error: " + ioa.getMessage());
+            } else {
+                System.out.println("Unknown payment error: " + e.getMessage());
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        processPaymentMethod("cash", "NONE");      // invalid payment method
+        processPaymentMethod("card", "UPI10");     // invalid offer for card
+        processPaymentMethod("upi", "UPI10");      // valid
+    }
+}

src/PaymentException.java

+public sealed class PaymentException extends Exception
+            permits InvalidPaymentMethodException, InvalidOfferAppliedException {
+
+        public PaymentException(String message) {
+            super(message);
+        }
+    }
+

src/PaymentService.java

+public class PaymentService {
+
+        public void paymentMethod(String method, String offer) throws PaymentException {
+            if (!method.equalsIgnoreCase("card") && !method.equalsIgnoreCase("upi")) {
+                throw new InvalidPaymentMethodException("Unsupported payment method: " + method);
+            }
+
+            if (method.equalsIgnoreCase("card") && offer.equalsIgnoreCase("UPI10")) {
+                throw new InvalidOfferAppliedException("Card payments do not support UPI10 offer.");
+            }
+
+            System.out.println("Payment successful using " + method + " with offer " + offer);
+        }
+    }
+

untitled.iml

+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>
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