[Java] better default value handling (#14130)

* add test for array default value

* update null return

* minor fixes

* move default value tests to echo api spec

* add new files

* remove unused files

* fix enum array default, add tests

* better array init

* Update modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java

Co-authored-by: Leonard Brünings <lord_damokles@gmx.net>

* Update modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java

Co-authored-by: Leonard Brünings <lord_damokles@gmx.net>

* revert the fix

* improve default value handling

* update native samples, add tests

* update samples

* fix tests

* use conditional test for timezone

* add tests to apache http client echo api

* add option to default container to null

* fix map default value

* minor refactoring

* update samples

* fix javadoc

* fix pom.xml

* add tests in java native echo client

* add java apache client echo tests

* fix test

* fix test

---------

Co-authored-by: Leonard Brünings <lord_damokles@gmx.net>

samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/AdditionalPropertiesClass.java

@@ -57,56 +57,56 @@ public class AdditionalPropertiesClass {
   // items.name=inner items.baseName=inner items.xmlName= items.xmlNamespace=
   // items.example= items.type=String
   @XmlElement(name = "inner")
-  private Map<String, String> mapString = null;
+  private Map<String, String> mapString = new HashMap<>();
 
   public static final String JSON_PROPERTY_MAP_NUMBER = "map_number";
   // Is a container wrapped=false
   // items.name=inner items.baseName=inner items.xmlName= items.xmlNamespace=
   // items.example= items.type=BigDecimal
   @XmlElement(name = "inner")
-  private Map<String, BigDecimal> mapNumber = null;
+  private Map<String, BigDecimal> mapNumber = new HashMap<>();
 
   public static final String JSON_PROPERTY_MAP_INTEGER = "map_integer";
   // Is a container wrapped=false
   // items.name=inner items.baseName=inner items.xmlName= items.xmlNamespace=
   // items.example= items.type=Integer
   @XmlElement(name = "inner")
-  private Map<String, Integer> mapInteger = null;
+  private Map<String, Integer> mapInteger = new HashMap<>();
 
   public static final String JSON_PROPERTY_MAP_BOOLEAN = "map_boolean";
   // Is a container wrapped=false
   // items.name=inner items.baseName=inner items.xmlName= items.xmlNamespace=
   // items.example= items.type=Boolean
   @XmlElement(name = "inner")
-  private Map<String, Boolean> mapBoolean = null;
+  private Map<String, Boolean> mapBoolean = new HashMap<>();
 
   public static final String JSON_PROPERTY_MAP_ARRAY_INTEGER = "map_array_integer";
   // Is a container wrapped=false
   // items.name=inner items.baseName=inner items.xmlName= items.xmlNamespace=
   // items.example= items.type=List&lt;Integer&gt;
   @XmlElement(name = "inner")
-  private Map<String, List<Integer>> mapArrayInteger = null;
+  private Map<String, List<Integer>> mapArrayInteger = new HashMap<>();
 
   public static final String JSON_PROPERTY_MAP_ARRAY_ANYTYPE = "map_array_anytype";
   // Is a container wrapped=false
   // items.name=inner items.baseName=inner items.xmlName= items.xmlNamespace=
   // items.example= items.type=List&lt;Object&gt;
   @XmlElement(name = "inner")
-  private Map<String, List<Object>> mapArrayAnytype = null;
+  private Map<String, List<Object>> mapArrayAnytype = new HashMap<>();
 
   public static final String JSON_PROPERTY_MAP_MAP_STRING = "map_map_string";
   // Is a container wrapped=false
   // items.name=inner items.baseName=inner items.xmlName= items.xmlNamespace=
   // items.example= items.type=Map&lt;String, String&gt;
   @XmlElement(name = "inner")
-  private Map<String, Map<String, String>> mapMapString = null;
+  private Map<String, Map<String, String>> mapMapString = new HashMap<>();
 
   public static final String JSON_PROPERTY_MAP_MAP_ANYTYPE = "map_map_anytype";
   // Is a container wrapped=false
   // items.name=inner items.baseName=inner items.xmlName= items.xmlNamespace=
   // items.example= items.type=Map&lt;String, Object&gt;
   @XmlElement(name = "inner")
-  private Map<String, Map<String, Object>> mapMapAnytype = null;
+  private Map<String, Map<String, Object>> mapMapAnytype = new HashMap<>();
 
   public static final String JSON_PROPERTY_ANYTYPE1 = "anytype_1";
   @XmlElement(name = "anytype_1")

samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/ArrayOfArrayOfNumberOnly.java

@@ -46,7 +46,7 @@ public class ArrayOfArrayOfNumberOnly {
   // items.name=arrayArrayNumber items.baseName=arrayArrayNumber items.xmlName= items.xmlNamespace=
   // items.example= items.type=List<BigDecimal>
   @XmlElement(name = "arrayArrayNumber")
-  private List<List<BigDecimal>> arrayArrayNumber = null;
+  private List<List<BigDecimal>> arrayArrayNumber = new ArrayList<>();
 
   public ArrayOfArrayOfNumberOnly() {
   }

samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/ArrayOfNumberOnly.java

@@ -46,7 +46,7 @@ public class ArrayOfNumberOnly {
   // items.name=arrayNumber items.baseName=arrayNumber items.xmlName= items.xmlNamespace=
   // items.example= items.type=BigDecimal
   @XmlElement(name = "arrayNumber")
-  private List<BigDecimal> arrayNumber = null;
+  private List<BigDecimal> arrayNumber = new ArrayList<>();
 
   public ArrayOfNumberOnly() {
   }

samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/ArrayTest.java

@@ -48,21 +48,21 @@ public class ArrayTest {
   // items.name=arrayOfString items.baseName=arrayOfString items.xmlName= items.xmlNamespace=
   // items.example= items.type=String
   @XmlElement(name = "arrayOfString")
-  private List<String> arrayOfString = null;
+  private List<String> arrayOfString = new ArrayList<>();
 
   public static final String JSON_PROPERTY_ARRAY_ARRAY_OF_INTEGER = "array_array_of_integer";
   // Is a container wrapped=false
   // items.name=arrayArrayOfInteger items.baseName=arrayArrayOfInteger items.xmlName= items.xmlNamespace=
   // items.example= items.type=List&lt;Long&gt;
   @XmlElement(name = "arrayArrayOfInteger")
-  private List<List<Long>> arrayArrayOfInteger = null;
+  private List<List<Long>> arrayArrayOfInteger = new ArrayList<>();
 
   public static final String JSON_PROPERTY_ARRAY_ARRAY_OF_MODEL = "array_array_of_model";
   // Is a container wrapped=false
   // items.name=arrayArrayOfModel items.baseName=arrayArrayOfModel items.xmlName= items.xmlNamespace=
   // items.example= items.type=List&lt;ReadOnlyFirst&gt;
   @XmlElement(name = "arrayArrayOfModel")
-  private List<List<ReadOnlyFirst>> arrayArrayOfModel = null;
+  private List<List<ReadOnlyFirst>> arrayArrayOfModel = new ArrayList<>();
 
   public ArrayTest() {
   }

samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/EnumArrays.java

@@ -128,7 +128,7 @@ public class EnumArrays {
   // items.name=arrayEnum items.baseName=arrayEnum items.xmlName= items.xmlNamespace=
   // items.example= items.type=String
   @XmlElement(name = "arrayEnum")
-  private List<ArrayEnumEnum> arrayEnum = null;
+  private List<ArrayEnumEnum> arrayEnum = new ArrayList<>();
 
   public EnumArrays() {
   }

samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/FileSchemaTestClass.java

@@ -51,7 +51,7 @@ public class FileSchemaTestClass {
   // items.name=files items.baseName=files items.xmlName= items.xmlNamespace=
   // items.example= items.type=ModelFile
   @XmlElement(name = "files")
-  private List<ModelFile> files = null;
+  private List<ModelFile> files = new ArrayList<>();
 
   public FileSchemaTestClass() {
   }

samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/MapTest.java

@@ -48,7 +48,7 @@ public class MapTest {
   // items.name=inner items.baseName=inner items.xmlName= items.xmlNamespace=
   // items.example= items.type=Map<String, String>
   @XmlElement(name = "inner")
-  private Map<String, Map<String, String>> mapMapOfString = null;
+  private Map<String, Map<String, String>> mapMapOfString = new HashMap<>();
 
   /**
    * Gets or Sets inner
@@ -94,21 +94,21 @@ public class MapTest {
   // items.name=inner items.baseName=inner items.xmlName= items.xmlNamespace=
   // items.example= items.type=String
   @XmlElement(name = "inner")
-  private Map<String, InnerEnum> mapOfEnumString = null;
+  private Map<String, InnerEnum> mapOfEnumString = new HashMap<>();
 
   public static final String JSON_PROPERTY_DIRECT_MAP = "direct_map";
   // Is a container wrapped=false
   // items.name=inner items.baseName=inner items.xmlName= items.xmlNamespace=
   // items.example= items.type=Boolean
   @XmlElement(name = "inner")
-  private Map<String, Boolean> directMap = null;
+  private Map<String, Boolean> directMap = new HashMap<>();
 
   public static final String JSON_PROPERTY_INDIRECT_MAP = "indirect_map";
   // Is a container wrapped=false
   // items.name=inner items.baseName=inner items.xmlName= items.xmlNamespace=
   // items.example= items.type=Boolean
   @XmlElement(name = "inner")
-  private Map<String, Boolean> indirectMap = null;
+  private Map<String, Boolean> indirectMap = new HashMap<>();
 
   public MapTest() {
   }

samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/MixedPropertiesAndAdditionalPropertiesClass.java

@@ -59,7 +59,7 @@ public class MixedPropertiesAndAdditionalPropertiesClass {
   // items.name=inner items.baseName=inner items.xmlName= items.xmlNamespace=
   // items.example= items.type=Animal
   @XmlElement(name = "inner")
-  private Map<String, Animal> map = null;
+  private Map<String, Animal> map = new HashMap<>();
 
   public MixedPropertiesAndAdditionalPropertiesClass() {
   }

samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/Pet.java

@@ -76,7 +76,7 @@ public class Pet {
   // items.example= items.type=Tag
   @XmlElement(name = "tags")
   @XmlElementWrapper(name = "tag")
-  private List<Tag> tags = null;
+  private List<Tag> tags = new ArrayList<>();
 
   /**
    * pet status in the store

samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/XmlItem.java

@@ -91,7 +91,7 @@ public class XmlItem {
   // items.example= items.type=Integer
   @XmlElement(name = "wrappedArray")
   @XmlElementWrapper(name = "wrapped_array")
-  private List<Integer> wrappedArray = null;
+  private List<Integer> wrappedArray = new ArrayList<>();
 
   public static final String JSON_PROPERTY_NAME_STRING = "name_string";
   @XmlElement(name = "xml_name_string")
@@ -114,7 +114,7 @@ public class XmlItem {
   // items.name=nameArray items.baseName=nameArray items.xmlName=xml_name_array_item items.xmlNamespace=
   // items.example= items.type=Integer
   @XmlElement(name = "xml_name_array_item")
-  private List<Integer> nameArray = null;
+  private List<Integer> nameArray = new ArrayList<>();
 
   public static final String JSON_PROPERTY_NAME_WRAPPED_ARRAY = "name_wrapped_array";
   // Is a container wrapped=true
@@ -122,7 +122,7 @@ public class XmlItem {
   // items.example= items.type=Integer
   @XmlElement(name = "xml_name_wrapped_array_item")
   @XmlElementWrapper(name = "xml_name_wrapped_array")
-  private List<Integer> nameWrappedArray = null;
+  private List<Integer> nameWrappedArray = new ArrayList<>();
 
   public static final String JSON_PROPERTY_PREFIX_STRING = "prefix_string";
   @XmlElement(name = "prefix_string")
@@ -145,7 +145,7 @@ public class XmlItem {
   // items.name=prefixArray items.baseName=prefixArray items.xmlName= items.xmlNamespace=
   // items.example= items.type=Integer
   @XmlElement(name = "prefixArray")
-  private List<Integer> prefixArray = null;
+  private List<Integer> prefixArray = new ArrayList<>();
 
   public static final String JSON_PROPERTY_PREFIX_WRAPPED_ARRAY = "prefix_wrapped_array";
   // Is a container wrapped=true
@@ -153,7 +153,7 @@ public class XmlItem {
   // items.example= items.type=Integer
   @XmlElement(name = "prefixWrappedArray")
   @XmlElementWrapper(name = "prefix_wrapped_array")
-  private List<Integer> prefixWrappedArray = null;
+  private List<Integer> prefixWrappedArray = new ArrayList<>();
 
   public static final String JSON_PROPERTY_NAMESPACE_STRING = "namespace_string";
   @XmlElement(namespace="http://a.com/schema", name = "namespace_string")
@@ -176,7 +176,7 @@ public class XmlItem {
   // items.name=namespaceArray items.baseName=namespaceArray items.xmlName= items.xmlNamespace=http://e.com/schema
   // items.example= items.type=Integer
   @XmlElement(namespace="http://e.com/schema", name = "namespaceArray")
-  private List<Integer> namespaceArray = null;
+  private List<Integer> namespaceArray = new ArrayList<>();
 
   public static final String JSON_PROPERTY_NAMESPACE_WRAPPED_ARRAY = "namespace_wrapped_array";
   // Is a container wrapped=true
@@ -184,7 +184,7 @@ public class XmlItem {
   // items.example= items.type=Integer
   @XmlElement(namespace="http://g.com/schema", name = "namespaceWrappedArray")
   @XmlElementWrapper(namespace="http://f.com/schema", name = "namespace_wrapped_array")
-  private List<Integer> namespaceWrappedArray = null;
+  private List<Integer> namespaceWrappedArray = new ArrayList<>();
 
   public static final String JSON_PROPERTY_PREFIX_NS_STRING = "prefix_ns_string";
   @XmlElement(namespace="http://a.com/schema", name = "prefix_ns_string")
@@ -207,7 +207,7 @@ public class XmlItem {
   // items.name=prefixNsArray items.baseName=prefixNsArray items.xmlName= items.xmlNamespace=http://e.com/schema
   // items.example= items.type=Integer
   @XmlElement(namespace="http://e.com/schema", name = "prefixNsArray")
-  private List<Integer> prefixNsArray = null;
+  private List<Integer> prefixNsArray = new ArrayList<>();
 
   public static final String JSON_PROPERTY_PREFIX_NS_WRAPPED_ARRAY = "prefix_ns_wrapped_array";
   // Is a container wrapped=true
@@ -215,7 +215,7 @@ public class XmlItem {
   // items.example= items.type=Integer
   @XmlElement(namespace="http://g.com/schema", name = "prefixNsWrappedArray")
   @XmlElementWrapper(namespace="http://f.com/schema", name = "prefix_ns_wrapped_array")
-  private List<Integer> prefixNsWrappedArray = null;
+  private List<Integer> prefixNsWrappedArray = new ArrayList<>();
 
   public XmlItem() {
   }