[Java] remove initialization for optional list property (#5363)

* set list to null in java if not required

* update petstore sample for java server stub

* update sample for msf4j

* add null assignment to new list/map in java

samples/server/petstore/java-inflector/src/gen/java/io/swagger/model/AdditionalPropertiesClass.java

@@ -16,10 +16,10 @@ import java.util.Map;
 
 public class AdditionalPropertiesClass   {
   @JsonProperty("map_property")
-  private Map<String, String> mapProperty = new HashMap<String, String>();
+  private Map<String, String> mapProperty = null;
 
   @JsonProperty("map_of_map_property")
-  private Map<String, Map<String, String>> mapOfMapProperty = new HashMap<String, Map<String, String>>();
+  private Map<String, Map<String, String>> mapOfMapProperty = null;
 
   /**
    **/

samples/server/petstore/java-inflector/src/gen/java/io/swagger/model/ArrayOfArrayOfNumberOnly.java

@@ -16,7 +16,7 @@ import java.util.List;
 
 public class ArrayOfArrayOfNumberOnly   {
   @JsonProperty("ArrayArrayNumber")
-  private List<List<BigDecimal>> arrayArrayNumber = new ArrayList<List<BigDecimal>>();
+  private List<List<BigDecimal>> arrayArrayNumber = null;
 
   /**
    **/

samples/server/petstore/java-inflector/src/gen/java/io/swagger/model/ArrayOfNumberOnly.java

@@ -16,7 +16,7 @@ import java.util.List;
 
 public class ArrayOfNumberOnly   {
   @JsonProperty("ArrayNumber")
-  private List<BigDecimal> arrayNumber = new ArrayList<BigDecimal>();
+  private List<BigDecimal> arrayNumber = null;
 
   /**
    **/

samples/server/petstore/java-inflector/src/gen/java/io/swagger/model/ArrayTest.java

@@ -16,13 +16,13 @@ import java.util.List;
 
 public class ArrayTest   {
   @JsonProperty("array_of_string")
-  private List<String> arrayOfString = new ArrayList<String>();
+  private List<String> arrayOfString = null;
 
   @JsonProperty("array_array_of_integer")
-  private List<List<Long>> arrayArrayOfInteger = new ArrayList<List<Long>>();
+  private List<List<Long>> arrayArrayOfInteger = null;
 
   @JsonProperty("array_array_of_model")
-  private List<List<ReadOnlyFirst>> arrayArrayOfModel = new ArrayList<List<ReadOnlyFirst>>();
+  private List<List<ReadOnlyFirst>> arrayArrayOfModel = null;
 
   /**
    **/

samples/server/petstore/java-inflector/src/gen/java/io/swagger/model/EnumArrays.java

@@ -81,7 +81,7 @@ public class EnumArrays   {
   }
 
   @JsonProperty("array_enum")
-  private List<ArrayEnumEnum> arrayEnum = new ArrayList<ArrayEnumEnum>();
+  private List<ArrayEnumEnum> arrayEnum = null;
 
   /**
    **/

samples/server/petstore/java-inflector/src/gen/java/io/swagger/model/MapTest.java

@@ -17,7 +17,7 @@ import java.util.Map;
 
 public class MapTest   {
   @JsonProperty("map_map_of_string")
-  private Map<String, Map<String, String>> mapMapOfString = new HashMap<String, Map<String, String>>();
+  private Map<String, Map<String, String>> mapMapOfString = null;
 
   /**
    * Gets or Sets inner
@@ -51,7 +51,7 @@ public class MapTest   {
   }
 
   @JsonProperty("map_of_enum_string")
-  private Map<String, InnerEnum> mapOfEnumString = new HashMap<String, InnerEnum>();
+  private Map<String, InnerEnum> mapOfEnumString = null;
 
   /**
    **/

samples/server/petstore/java-inflector/src/gen/java/io/swagger/model/MixedPropertiesAndAdditionalPropertiesClass.java

@@ -25,7 +25,7 @@ public class MixedPropertiesAndAdditionalPropertiesClass   {
   private Date dateTime = null;
 
   @JsonProperty("map")
-  private Map<String, Animal> map = new HashMap<String, Animal>();
+  private Map<String, Animal> map = null;
 
   /**
    **/

samples/server/petstore/java-inflector/src/gen/java/io/swagger/model/Pet.java

@@ -30,7 +30,7 @@ public class Pet   {
   private List<String> photoUrls = new ArrayList<String>();
 
   @JsonProperty("tags")
-  private List<Tag> tags = new ArrayList<Tag>();
+  private List<Tag> tags = null;
 
   /**
    * pet status in the store

samples/server/petstore/java-inflector/src/main/swagger/swagger.yaml

@@ -109,11 +109,11 @@ paths:
         type: "array"
         items:
           type: "string"
+          default: "available"
           enum:
           - "available"
           - "pending"
           - "sold"
-          default: "available"
         collectionFormat: "csv"
       responses:
         200:
@@ -623,10 +623,10 @@ paths:
         type: "array"
         items:
           type: "string"
+          default: "$"
           enum:
           - ">"
           - "$"
-          default: "$"
       - name: "enum_form_string"
         in: "formData"
         description: "Form parameter enum test (string)"
@@ -644,10 +644,10 @@ paths:
         type: "array"
         items:
           type: "string"
+          default: "$"
           enum:
           - ">"
           - "$"
-          default: "$"
       - name: "enum_header_string"
         in: "header"
         description: "Header parameter enum test (string)"
@@ -665,10 +665,10 @@ paths:
         type: "array"
         items:
           type: "string"
+          default: "$"
           enum:
           - ">"
           - "$"
-          default: "$"
       - name: "enum_query_string"
         in: "query"
         description: "Query parameter enum test (string)"