feat: 404 Added getDefaultValue to Codec

pbj-core/pbj-compiler/src/main/java/com/hedera/pbj/compiler/impl/generators/TestGenerator.java

@@ -406,6 +406,13 @@ public void testTestEqualsAndHashCode() throws Exception {
                         assertNotEquals(item2HashCode, item3HashCode);
                     }
                 }
+
+                @Test
+                public void testCodecGetDefaultValueMethod(){
+                    final var codec = $modelClassName.PROTOBUF;
+                    final var codecDefaultValue = codec.getDefaultValue();
+                    assertEquals($modelClassName.DEFAULT, codecDefaultValue);
+                }
                 """
                 .replace("$modelClassName",modelClassName)
                 .replace("$protocModelClass",protoCJavaFullQualifiedClass)

pbj-core/pbj-compiler/src/main/java/com/hedera/pbj/compiler/impl/generators/protobuf/CodecDefaultInstanceMethodGenerator.java

@@ -0,0 +1,24 @@
+package com.hedera.pbj.compiler.impl.generators.protobuf;
+
+import static com.hedera.pbj.compiler.impl.Common.DEFAULT_INDENT;
+
+
+/**
+ * Generates the getDefaultInstance method for the codec.
+ */
+public class CodecDefaultInstanceMethodGenerator {
+
+    static String generateGetDefaultInstanceMethod() {
+        return """
+            /**
+             * Get the default value for the model class.
+             *
+             * @return The default value for the model class
+             */
+            public $modelClass getDefaultInstance() {
+                return $modelClass.getDefaultInstance();
+            }
+            """
+            .indent(DEFAULT_INDENT);
+    }
+}

pbj-core/pbj-compiler/src/main/java/com/hedera/pbj/compiler/impl/generators/protobuf/CodecGenerator.java

@@ -19,6 +19,8 @@
 import java.util.TreeSet;
 import java.util.stream.Collectors;
 
+import static com.hedera.pbj.compiler.impl.generators.protobuf.CodecDefaultInstanceMethodGenerator.generateGetDefaultInstanceMethod;
+
 /**
  * Code generator that parses protobuf files and generates writers for each message type.
  */
@@ -105,6 +107,7 @@ public final class $codecClass implements Codec<$modelClass> {
                     $measureDataMethod
                     $measureRecordMethod
                     $fastEqualsMethod
+                    $getDefaultInstanceMethod
                     }
                     """
                     .replace("$package", codecPackage)
@@ -121,6 +124,7 @@ public final class $codecClass implements Codec<$modelClass> {
                     .replace("$measureDataMethod", CodecMeasureDataMethodGenerator.generateMeasureMethod(modelClassName, fields))
                     .replace("$measureRecordMethod", CodecMeasureRecordMethodGenerator.generateMeasureMethod(modelClassName, fields))
                     .replace("$fastEqualsMethod", CodecFastEqualsMethodGenerator.generateFastEqualsMethod(modelClassName, fields))
+                    .replace("$getDefaultInstanceMethod", generateGetDefaultInstanceMethod())
             );
         // spotless:on
         }