Fix some code issues to pass Sonar quality gate

cli/src/main/java/org/openapitools/openapidiff/cli/Main.java

@@ -2,6 +2,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import org.apache.commons.cli.CommandLine;
 import org.apache.commons.cli.CommandLineParser;
 import org.apache.commons.cli.DefaultParser;
@@ -100,7 +101,6 @@ public static void main(String... args) {
             .desc("export diff as text in given file")
             .build());
 
-    final String message = "Hello logging!";
     // create the parser
     CommandLineParser parser = new DefaultParser();
     try {
@@ -202,7 +202,7 @@ private static void writeOutput(String output, String outputFile) {
     File file = new File(outputFile);
     logger.debug("Output file: {}", file.getAbsolutePath());
     try {
-      FileUtils.writeStringToFile(file, output);
+      FileUtils.writeStringToFile(file, output, StandardCharsets.UTF_8);
     } catch (IOException e) {
       logger.error("Impossible to write output to file {}", outputFile, e);
       System.exit(2);

core/src/main/java/org/openapitools/openapidiff/core/OpenApiCompare.java

@@ -11,8 +11,8 @@
 
 public class OpenApiCompare {
 
-  private static OpenAPIParser openApiParser = new OpenAPIParser();
-  private static ParseOptions options = new ParseOptions();
+  private static final OpenAPIParser openApiParser = new OpenAPIParser();
+  private static final ParseOptions options = new ParseOptions();
 
   static {
     options.setResolve(true);

core/src/main/java/org/openapitools/openapidiff/core/compare/ApiResponseDiff.java

@@ -14,7 +14,7 @@
 
 /** Created by adarsh.sharma on 04/01/18. */
 public class ApiResponseDiff {
-  private OpenApiDiff openApiDiff;
+  private final OpenApiDiff openApiDiff;
 
   public ApiResponseDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;

core/src/main/java/org/openapitools/openapidiff/core/compare/ContentDiff.java

@@ -10,19 +10,14 @@
 import org.openapitools.openapidiff.core.model.ChangedMediaType;
 import org.openapitools.openapidiff.core.model.DiffContext;
 
-public class ContentDiff implements Comparable<Content> {
+public class ContentDiff {
 
-  private OpenApiDiff openApiDiff;
+  private final OpenApiDiff openApiDiff;
 
   public ContentDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;
   }
 
-  @Override
-  public boolean compare(Content left, Content right) {
-    return false;
-  }
-
   public Optional<ChangedContent> diff(Content left, Content right, DiffContext context) {
 
     MapKeyDiff<String, MediaType> mediaTypeDiff = MapKeyDiff.diff(left, right);

core/src/main/java/org/openapitools/openapidiff/core/compare/ExtensionsDiff.java

@@ -13,20 +13,20 @@
 public class ExtensionsDiff {
   private final OpenApiDiff openApiDiff;
 
-  private ServiceLoader<ExtensionDiff> extensionsLoader = ServiceLoader.load(ExtensionDiff.class);
-  private List<ExtensionDiff> extensionsDiff = new ArrayList<>();
+  private final List<ExtensionDiff> extensionDiffs = new ArrayList<>();
 
   public ExtensionsDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;
-    this.extensionsLoader.reload();
-    for (ExtensionDiff anExtensionsLoader : this.extensionsLoader) {
-      extensionsDiff.add(anExtensionsLoader);
+    ServiceLoader<ExtensionDiff> extensionsLoader = ServiceLoader.load(ExtensionDiff.class);
+    extensionsLoader.reload();
+    for (ExtensionDiff anExtensionsLoader : extensionsLoader) {
+      extensionDiffs.add(anExtensionsLoader);
     }
   }
 
   public boolean isParentApplicable(
       Change.Type type, Object parent, Map<String, Object> extensions, DiffContext context) {
-    if (extensions.size() == 0) {
+    if (extensions.isEmpty()) {
       return true;
     }
     return extensions.entrySet().stream()
@@ -40,7 +40,7 @@ public boolean isParentApplicable(
   }
 
   public Optional<ExtensionDiff> getExtensionDiff(String name) {
-    return extensionsDiff.stream().filter(diff -> ("x-" + diff.getName()).equals(name)).findFirst();
+    return extensionDiffs.stream().filter(diff -> ("x-" + diff.getName()).equals(name)).findFirst();
   }
 
   public <T> Optional<T> executeExtension(String name, Function<ExtensionDiff, T> predicate) {

core/src/main/java/org/openapitools/openapidiff/core/compare/HeaderDiff.java

@@ -14,10 +14,10 @@
 
 /** Created by adarsh.sharma on 28/12/17. */
 public class HeaderDiff extends ReferenceDiffCache<Header, ChangedHeader> {
-  private static RefPointer<Header> refPointer = new RefPointer<>(RefType.HEADERS);
-  private OpenApiDiff openApiDiff;
-  private Components leftComponents;
-  private Components rightComponents;
+  private static final RefPointer<Header> refPointer = new RefPointer<>(RefType.HEADERS);
+  private final OpenApiDiff openApiDiff;
+  private final Components leftComponents;
+  private final Components rightComponents;
 
   public HeaderDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;

core/src/main/java/org/openapitools/openapidiff/core/compare/HeadersDiff.java

@@ -13,7 +13,7 @@
 
 /** Created by adarsh.sharma on 28/12/17. */
 public class HeadersDiff {
-  private OpenApiDiff openApiDiff;
+  private final OpenApiDiff openApiDiff;
 
   public HeadersDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;

core/src/main/java/org/openapitools/openapidiff/core/compare/MapKeyDiff.java

@@ -15,7 +15,7 @@ public class MapKeyDiff<K, V> {
 
   private Map<K, V> increased;
   private Map<K, V> missing;
-  private List<K> sharedKey;
+  private final List<K> sharedKey;
 
   private MapKeyDiff() {
     this.sharedKey = new ArrayList<>();

core/src/main/java/org/openapitools/openapidiff/core/compare/MetadataDiff.java

@@ -9,9 +9,9 @@
 
 public class MetadataDiff {
 
-  private Components leftComponents;
-  private Components rightComponents;
-  private OpenApiDiff openApiDiff;
+  private final Components leftComponents;
+  private final Components rightComponents;
+  private final OpenApiDiff openApiDiff;
 
   public MetadataDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;

core/src/main/java/org/openapitools/openapidiff/core/compare/OAuthFlowDiff.java

@@ -11,7 +11,7 @@
 
 /** Created by adarsh.sharma on 12/01/18. */
 public class OAuthFlowDiff {
-  private OpenApiDiff openApiDiff;
+  private final OpenApiDiff openApiDiff;
 
   public OAuthFlowDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;

core/src/main/java/org/openapitools/openapidiff/core/compare/OAuthFlowsDiff.java

@@ -10,7 +10,7 @@
 
 /** Created by adarsh.sharma on 12/01/18. */
 public class OAuthFlowsDiff {
-  private OpenApiDiff openApiDiff;
+  private final OpenApiDiff openApiDiff;
 
   public OAuthFlowsDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;

core/src/main/java/org/openapitools/openapidiff/core/compare/OperationDiff.java

@@ -13,7 +13,7 @@
 
 /** Created by adarsh.sharma on 04/01/18. */
 public class OperationDiff {
-  private OpenApiDiff openApiDiff;
+  private final OpenApiDiff openApiDiff;
 
   public OperationDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;
@@ -70,7 +70,7 @@ public Optional<ChangedOperation> diff(
     openApiDiff
         .getExtensionsDiff()
         .diff(oldOperation.getExtensions(), newOperation.getExtensions(), context)
-        .ifPresent(extensions -> changedOperation.setExtensions(extensions));
+        .ifPresent(changedOperation::setExtensions);
 
     return isChanged(changedOperation);
   }

core/src/main/java/org/openapitools/openapidiff/core/compare/ParameterDiff.java

@@ -14,10 +14,10 @@
 
 public class ParameterDiff extends ReferenceDiffCache<Parameter, ChangedParameter> {
 
-  private static RefPointer<Parameter> refPointer = new RefPointer<>(RefType.PARAMETERS);
-  private Components leftComponents;
-  private Components rightComponents;
-  private OpenApiDiff openApiDiff;
+  private static final RefPointer<Parameter> refPointer = new RefPointer<>(RefType.PARAMETERS);
+  private final Components leftComponents;
+  private final Components rightComponents;
+  private final OpenApiDiff openApiDiff;
 
   public ParameterDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;

core/src/main/java/org/openapitools/openapidiff/core/compare/ParametersDiff.java

@@ -19,11 +19,11 @@
  * @author QDesrame
  */
 public class ParametersDiff {
+  private static final RefPointer<Parameter> refPointer = new RefPointer<>(RefType.PARAMETERS);
 
-  private Components leftComponents;
-  private Components rightComponents;
-  private OpenApiDiff openApiDiff;
-  private static RefPointer<Parameter> refPointer = new RefPointer<>(RefType.PARAMETERS);
+  private final Components leftComponents;
+  private final Components rightComponents;
+  private final OpenApiDiff openApiDiff;
 
   public ParametersDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;

core/src/main/java/org/openapitools/openapidiff/core/compare/PathDiff.java

@@ -11,7 +11,7 @@
 import org.openapitools.openapidiff.core.model.DiffContext;
 
 public class PathDiff {
-  private OpenApiDiff openApiDiff;
+  private final OpenApiDiff openApiDiff;
 
   public PathDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;

core/src/main/java/org/openapitools/openapidiff/core/compare/PathsDiff.java

@@ -12,7 +12,7 @@
 
 public class PathsDiff {
   private static final String REGEX_PATH = "\\{([^/]+)\\}";
-  private OpenApiDiff openApiDiff;
+  private final OpenApiDiff openApiDiff;
 
   public PathsDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;

core/src/main/java/org/openapitools/openapidiff/core/compare/ReferenceDiffCache.java

@@ -8,7 +8,7 @@
 
 /** Created by adarsh.sharma on 07/01/18. */
 public abstract class ReferenceDiffCache<C, D> {
-  private Map<CacheKey, D> refDiffMap;
+  private final Map<CacheKey, D> refDiffMap;
 
   public ReferenceDiffCache() {
     this.refDiffMap = new HashMap<>();

core/src/main/java/org/openapitools/openapidiff/core/compare/RequestBodyDiff.java

@@ -15,8 +15,9 @@
 
 /** Created by adarsh.sharma on 28/12/17. */
 public class RequestBodyDiff extends ReferenceDiffCache<RequestBody, ChangedRequestBody> {
-  private static RefPointer<RequestBody> refPointer = new RefPointer<>(RefType.REQUEST_BODIES);
-  private OpenApiDiff openApiDiff;
+  private static final RefPointer<RequestBody> refPointer =
+      new RefPointer<>(RefType.REQUEST_BODIES);
+  private final OpenApiDiff openApiDiff;
 
   public RequestBodyDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;

core/src/main/java/org/openapitools/openapidiff/core/compare/ResponseDiff.java

@@ -13,10 +13,10 @@
 
 /** Created by adarsh.sharma on 28/12/17. */
 public class ResponseDiff extends ReferenceDiffCache<ApiResponse, ChangedResponse> {
-  private static RefPointer<ApiResponse> refPointer = new RefPointer<>(RefType.RESPONSES);
-  private OpenApiDiff openApiDiff;
-  private Components leftComponents;
-  private Components rightComponents;
+  private static final RefPointer<ApiResponse> refPointer = new RefPointer<>(RefType.RESPONSES);
+  private final OpenApiDiff openApiDiff;
+  private final Components leftComponents;
+  private final Components rightComponents;
 
   public ResponseDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;

core/src/main/java/org/openapitools/openapidiff/core/compare/SchemaDiff.java

@@ -26,8 +26,8 @@
 
 public class SchemaDiff extends ReferenceDiffCache<Schema, ChangedSchema> {
 
-  private static RefPointer<Schema> refPointer = new RefPointer<>(RefType.SCHEMAS);
-  private static Map<Class<? extends Schema>, Class<? extends SchemaDiffResult>>
+  private static final RefPointer<Schema> refPointer = new RefPointer<>(RefType.SCHEMAS);
+  private static final Map<Class<? extends Schema>, Class<? extends SchemaDiffResult>>
       schemaDiffResultClassMap = new LinkedHashMap<>();
 
   static {
@@ -36,9 +36,9 @@ public class SchemaDiff extends ReferenceDiffCache<Schema, ChangedSchema> {
     schemaDiffResultClassMap.put(ComposedSchema.class, ComposedSchemaDiffResult.class);
   }
 
-  private Components leftComponents;
-  private Components rightComponents;
-  private OpenApiDiff openApiDiff;
+  private final Components leftComponents;
+  private final Components rightComponents;
+  private final OpenApiDiff openApiDiff;
 
   public SchemaDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;

core/src/main/java/org/openapitools/openapidiff/core/compare/SecurityRequirementDiff.java

@@ -7,14 +7,13 @@
 import io.swagger.v3.oas.models.security.SecurityScheme;
 import java.util.*;
 import org.openapitools.openapidiff.core.model.ChangedSecurityRequirement;
-import org.openapitools.openapidiff.core.model.ChangedSecurityScheme;
 import org.openapitools.openapidiff.core.model.DiffContext;
 
 /** Created by adarsh.sharma on 07/01/18. */
 public class SecurityRequirementDiff {
-  private OpenApiDiff openApiDiff;
-  private Components leftComponents;
-  private Components rightComponents;
+  private final OpenApiDiff openApiDiff;
+  private final Components leftComponents;
+  private final Components rightComponents;
 
   public SecurityRequirementDiff(OpenApiDiff openApiDiff) {
     this.openApiDiff = openApiDiff;
@@ -30,8 +29,7 @@ public SecurityRequirementDiff(OpenApiDiff openApiDiff) {
 
   public static SecurityRequirement getCopy(LinkedHashMap<String, List<String>> right) {
     SecurityRequirement newSecurityRequirement = new SecurityRequirement();
-    right.entrySet().stream()
-        .forEach(e -> newSecurityRequirement.put(e.getKey(), new ArrayList<>(e.getValue())));
+    right.forEach((key, value) -> newSecurityRequirement.put(key, new ArrayList<>(value)));
     return newSecurityRequirement;
   }
 
@@ -68,29 +66,31 @@ public Optional<ChangedSecurityRequirement> diff(
     ChangedSecurityRequirement changedSecurityRequirement =
         new ChangedSecurityRequirement(left, right != null ? getCopy(right) : null);
 
-    left = left == null ? new SecurityRequirement() : left;
-    right = right == null ? new SecurityRequirement() : right;
+    SecurityRequirement leftRequirement = left == null ? new SecurityRequirement() : left;
+    SecurityRequirement rightRequirement = right == null ? new SecurityRequirement() : right;
 
-    for (String leftSchemeRef : left.keySet()) {
-      LinkedHashMap<String, List<String>> rightSec = contains(right, leftSchemeRef);
+    for (Map.Entry<String, List<String>> leftEntry : leftRequirement.entrySet()) {
+      LinkedHashMap<String, List<String>> rightSec = contains(rightRequirement, leftEntry.getKey());
       if (rightSec.isEmpty()) {
-        changedSecurityRequirement.addMissing(leftSchemeRef, left.get(leftSchemeRef));
+        changedSecurityRequirement.addMissing(leftEntry.getKey(), leftEntry.getValue());
       } else {
-        String rightSchemeRef = rightSec.keySet().stream().findFirst().get();
-        right.remove(rightSchemeRef);
-        Optional<ChangedSecurityScheme> diff =
-            openApiDiff
-                .getSecuritySchemeDiff()
-                .diff(
-                    leftSchemeRef,
-                    left.get(leftSchemeRef),
-                    rightSchemeRef,
-                    rightSec.get(rightSchemeRef),
-                    context);
-        diff.ifPresent(changedSecurityRequirement::addChanged);
+        Optional<String> rightSchemeRef = rightSec.keySet().stream().findFirst();
+        rightSchemeRef.ifPresent(rightRequirement::remove);
+        rightSchemeRef
+            .flatMap(
+                rightScheme ->
+                    openApiDiff
+                        .getSecuritySchemeDiff()
+                        .diff(
+                            leftEntry.getKey(),
+                            leftEntry.getValue(),
+                            rightScheme,
+                            rightSec.get(rightScheme),
+                            context))
+            .ifPresent(changedSecurityRequirement::addChanged);
       }
     }
-    right.forEach(changedSecurityRequirement::addIncreased);
+    rightRequirement.forEach(changedSecurityRequirement::addIncreased);
 
     return isChanged(changedSecurityRequirement);
   }