[Java] Use html entities in javadoc of generated code

[jmini]

PR checklist

• Read the contribution guidelines.
• Ran the shell script bin/java-petstore-all.sh
• Filed the PR against the correct branch: Default: master.
• Copied the technical committee to review the pull request if your PR is targeting a particular programming language.

cc @bbdouglas (2017/07) @JFCote (2017/08) @sreeshas (2017/08) @jfiala (2017/08) @lukoyanov (2017/09) @cbornet (2017/09) @jeff9finger (2018/01)

Description of the PR

Fix for #43: the javadoc should use html entities like ArrayList<String> and not ArrayList<String> for the maven build of the generated project to run without issue.

[jmini]

To test it you can run the java codegen on petstore.json like this:

        JavaClientCodegen config = new org.openapitools.codegen.languages.JavaClientCodegen();
        config.setArtifactId(artifactId);
        config.setJava8Mode(true);

        Path outputDirPath = Paths.get(outputDir);

        config.setHideGenerationTimestamp(true);
        config.setOutputDir(outputDir);

        final OpenAPIParser openApiParser = new OpenAPIParser();
        final ParseOptions options = new ParseOptions();
        final OpenAPI openAPI = openApiParser.readLocation(inputSpec, null, options).getOpenAPI();

        final ClientOptInput opts = new ClientOptInput();
        opts.setConfig(config);
        opts.setOpenAPI(openAPI);
        opts.setOpts(new ClientOpts());
        new DefaultGenerator().opts(opts).generate();

I get this change before and after the change:

--- a/org/openapitools/client/api/PetApi.java
+++ b/org/openapitools/client/api/PetApi.java
@@ -295,7 +295,7 @@ public class PetApi {
     }
     /**
      * Build call for findPetsByStatus
-     * @param status Status values that need to be considered for filter (optional, default to new ArrayList<String>())
+     * @param status Status values that need to be considered for filter (optional, default to new ArrayList&lt;String&gt;())
      * @param progressListener Progress listener
      * @param progressRequestListener Progress request listener
      * @return Call to execute
@@ -356,7 +356,7 @@ public class PetApi {
     /**
      * Finds Pets by status
      * Multiple status values can be provided with comma separated strings
-     * @param status Status values that need to be considered for filter (optional, default to new ArrayList<String>())
+     * @param status Status values that need to be considered for filter (optional, default to new ArrayList&lt;String&gt;())
      * @return List&lt;Pet&gt;
      * @throws ApiException If fail to call the API, e.g. server error or cannot deserialize the response body
      */
@@ -368,7 +368,7 @@ public class PetApi {
     /**
      * Finds Pets by status
      * Multiple status values can be provided with comma separated strings
-     * @param status Status values that need to be considered for filter (optional, default to new ArrayList<String>())
+     * @param status Status values that need to be considered for filter (optional, default to new ArrayList&lt;String&gt;())
      * @return ApiResponse&lt;List&lt;Pet&gt;&gt;
      * @throws ApiException If fail to call the API, e.g. server error or cannot deserialize the response body
      */
@@ -381,7 +381,7 @@ public class PetApi {
     /**
      * Finds Pets by status (asynchronously)
      * Multiple status values can be provided with comma separated strings
-     * @param status Status values that need to be considered for filter (optional, default to new ArrayList<String>())
+     * @param status Status values that need to be considered for filter (optional, default to new ArrayList&lt;String&gt;())
      * @param callback The callback to be executed when the API call finishes
      * @return The request call
      * @throws ApiException If fail to process the API call, e.g. serializing the request body object

[wing328]

I'll check to see if we need to do something similar to C# templates.