diff --git a/modules/openapi-generator/src/main/resources/Java/JSON.mustache b/modules/openapi-generator/src/main/resources/Java/JSON.mustache
index b951c3c555db..723ea79f16e4 100644
--- a/modules/openapi-generator/src/main/resources/Java/JSON.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/JSON.mustache
@@ -69,7 +69,7 @@ public class JSON {
                 .registerTypeSelector({{classname}}.class, new TypeSelector() {
                     @Override
                     public Class getClassForElement(JsonElement readElement) {
-                        Map classByDiscriminatorValue = new HashMap();
+                        Map<String, Class> classByDiscriminatorValue = new HashMap<String, Class>();
                         {{#mappedModels}}
                         classByDiscriminatorValue.put("{{mappingName}}".toUpperCase(Locale.ROOT), {{modelName}}.class);
                         {{/mappedModels}}
diff --git a/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/pom.mustache b/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/pom.mustache
index c11b4ab127d7..788d416e0482 100644
--- a/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/pom.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/pom.mustache
@@ -40,6 +40,19 @@
 
     <build>
         <plugins>
+           <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.8.1</version>
+                <configuration>
+                    <fork>true</fork>
+                    <meminitial>128m</meminitial>
+                    <maxmem>512m</maxmem>
+                    <compilerArgs>
+                        <arg>-Xlint:all</arg>
+                    </compilerArgs>
+                </configuration>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-enforcer-plugin</artifactId>
diff --git a/modules/openapi-generator/src/main/resources/Java/pom.mustache b/modules/openapi-generator/src/main/resources/Java/pom.mustache
index dd95ac7554ee..28dfab1f2575 100644
--- a/modules/openapi-generator/src/main/resources/Java/pom.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/pom.mustache
@@ -40,6 +40,20 @@
 
     <build>
         <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.8.1</version>
+                <configuration>
+                    <fork>true</fork>
+                    <meminitial>128m</meminitial>
+                    <maxmem>512m</maxmem>
+                    <compilerArgs>
+                        <arg>-Xlint:all</arg>
+                    </compilerArgs>
+                </configuration>
+            </plugin>
+
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-enforcer-plugin</artifactId>
diff --git a/samples/client/petstore/java/jersey1/pom.xml b/samples/client/petstore/java/jersey1/pom.xml
index 407d9056d9c1..9cf21702ab49 100644
--- a/samples/client/petstore/java/jersey1/pom.xml
+++ b/samples/client/petstore/java/jersey1/pom.xml
@@ -33,6 +33,20 @@
 
     <build>
         <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.8.1</version>
+                <configuration>
+                    <fork>true</fork>
+                    <meminitial>128m</meminitial>
+                    <maxmem>512m</maxmem>
+                    <compilerArgs>
+                        <arg>-Xlint:all</arg>
+                    </compilerArgs>
+                </configuration>
+            </plugin>
+
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-enforcer-plugin</artifactId>
diff --git a/samples/client/petstore/java/okhttp-gson-parcelableModel/pom.xml b/samples/client/petstore/java/okhttp-gson-parcelableModel/pom.xml
index d43fd33d990f..e173a9dce40a 100644
--- a/samples/client/petstore/java/okhttp-gson-parcelableModel/pom.xml
+++ b/samples/client/petstore/java/okhttp-gson-parcelableModel/pom.xml
@@ -33,6 +33,19 @@
 
     <build>
         <plugins>
+           <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.8.1</version>
+                <configuration>
+                    <fork>true</fork>
+                    <meminitial>128m</meminitial>
+                    <maxmem>512m</maxmem>
+                    <compilerArgs>
+                        <arg>-Xlint:all</arg>
+                    </compilerArgs>
+                </configuration>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-enforcer-plugin</artifactId>
diff --git a/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/JSON.java b/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/JSON.java
index 3f214bf1fbf4..a745ed9fd89a 100644
--- a/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/JSON.java
+++ b/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/JSON.java
@@ -55,7 +55,7 @@ public static GsonBuilder createGson() {
                 .registerTypeSelector(Animal.class, new TypeSelector() {
                     @Override
                     public Class getClassForElement(JsonElement readElement) {
-                        Map classByDiscriminatorValue = new HashMap();
+                        Map<String, Class> classByDiscriminatorValue = new HashMap<String, Class>();
                         classByDiscriminatorValue.put("Dog".toUpperCase(Locale.ROOT), Dog.class);
                         classByDiscriminatorValue.put("Cat".toUpperCase(Locale.ROOT), Cat.class);
                         classByDiscriminatorValue.put("BigCat".toUpperCase(Locale.ROOT), BigCat.class);
diff --git a/samples/client/petstore/java/okhttp-gson/pom.xml b/samples/client/petstore/java/okhttp-gson/pom.xml
index 4e40e0913c4e..d40436a6a306 100644
--- a/samples/client/petstore/java/okhttp-gson/pom.xml
+++ b/samples/client/petstore/java/okhttp-gson/pom.xml
@@ -33,6 +33,19 @@
 
     <build>
         <plugins>
+           <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.8.1</version>
+                <configuration>
+                    <fork>true</fork>
+                    <meminitial>128m</meminitial>
+                    <maxmem>512m</maxmem>
+                    <compilerArgs>
+                        <arg>-Xlint:all</arg>
+                    </compilerArgs>
+                </configuration>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-enforcer-plugin</artifactId>
diff --git a/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/JSON.java b/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/JSON.java
index 3f214bf1fbf4..a745ed9fd89a 100644
--- a/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/JSON.java
+++ b/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/JSON.java
@@ -55,7 +55,7 @@ public static GsonBuilder createGson() {
                 .registerTypeSelector(Animal.class, new TypeSelector() {
                     @Override
                     public Class getClassForElement(JsonElement readElement) {
-                        Map classByDiscriminatorValue = new HashMap();
+                        Map<String, Class> classByDiscriminatorValue = new HashMap<String, Class>();
                         classByDiscriminatorValue.put("Dog".toUpperCase(Locale.ROOT), Dog.class);
                         classByDiscriminatorValue.put("Cat".toUpperCase(Locale.ROOT), Cat.class);
                         classByDiscriminatorValue.put("BigCat".toUpperCase(Locale.ROOT), BigCat.class);
diff --git a/samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/JSON.java b/samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/JSON.java
index 3f214bf1fbf4..a745ed9fd89a 100644
--- a/samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/JSON.java
+++ b/samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/JSON.java
@@ -55,7 +55,7 @@ public static GsonBuilder createGson() {
                 .registerTypeSelector(Animal.class, new TypeSelector() {
                     @Override
                     public Class getClassForElement(JsonElement readElement) {
-                        Map classByDiscriminatorValue = new HashMap();
+                        Map<String, Class> classByDiscriminatorValue = new HashMap<String, Class>();
                         classByDiscriminatorValue.put("Dog".toUpperCase(Locale.ROOT), Dog.class);
                         classByDiscriminatorValue.put("Cat".toUpperCase(Locale.ROOT), Cat.class);
                         classByDiscriminatorValue.put("BigCat".toUpperCase(Locale.ROOT), BigCat.class);