Fix #1735: Add Java Linter to the project

.github/workflows/main.yml

@@ -6,12 +6,12 @@ on:
   workflow_dispatch:
   pull_request:
   push:
-    branches:    
+    branches:
       # Push events on develop branch
       - develop
 
 # This workflow has the following jobs:
-# linters: Kotlin and Protobuf Linting
+# linters: Kotlin, Protobuf and Java Linting
 # robolectric_tests: Robolectric tests for all modules except the app module
 # app_tests: Non-flaky Robolectric tests for the app module
 jobs:
@@ -25,40 +25,55 @@ jobs:
     steps:
     - uses: actions/checkout@v2
 
+    - name: Set up JDK 1.11
+      uses: actions/setup-java@v1
+      with:
+        java-version: 1.11
+
     - name: Download Ktlint
       run: |
         KTLINT="0.37.0"
         echo Using Ktlint $KTLINT
         curl -sSLO https://github.com/pinterest/ktlint/releases/download/$KTLINT/ktlint
         chmod a+x ktlint
-    
-    -  name: Download buf
-       run: |
+
+    - name: Download buf
+      run: |
         BUFVERSION="v0.15.0"
         echo Using Bufbuild version $BUFVERSION
         curl -sSL https://github.com/bufbuild/buf/releases/download/$BUFVERSION/buf-$(uname -s)-$(uname -m) > buf
         chmod a+x buf
-
+
+    - name: Download Checkstyle
+      run: |
+        CHECKSTYLE="8.37"
+        echo Using Checkstyle version $CHECKSTYLE
+        curl -sSLO https://github.com/checkstyle/checkstyle/releases/download/checkstyle-$CHECKSTYLE/checkstyle-$CHECKSTYLE-all.jar
+        chmod a+x checkstyle-$CHECKSTYLE-all.jar
+
     - name: Kotlin lint check
       run: ./ktlint --android domain/src/**/*.kt utility/src/**/*.kt data/src/**/*.kt app/src/**/*.kt testing/src/**/*.kt && echo "Lint completed successfully"
-
-    -  name: Protobuf lint check
-       run: ./buf check lint --input=model/src/main/proto --input-config buf.yaml && echo "Protobuf lint check completed successfully"
-
+
+    - name: Protobuf lint check
+      run: ./buf check lint --input=model/src/main/proto --input-config buf.yaml && echo "Protobuf lint check completed successfully"
+
+    - name: Java lint check
+      run: java -jar checkstyle-8.37-all.jar -c=checkstyle.xml app/src/**/*.java && echo "Lint completed successfully"
+
   robolectric_tests:
     name: Robolectric Tests (Non-App Modules)
     runs-on:  ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-18.04] 
+        os: [ubuntu-18.04]
     steps:
      - uses: actions/checkout@v2
      - uses: actions/cache@v2
        id: cache
        with:
          path: ~/.gradle
          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*') }}-jars-{{ checksum "build.gradle" }}
-         
+
      - name: Set up JDK 1.9
        uses: actions/setup-java@v1
        with:
@@ -67,11 +82,11 @@ jobs:
      - name: Install Dependencies
        if: steps.cache.outputs.cache-hit != 'true'
        run: ./gradlew --full-stacktrace androidDependencies
-     
+
      - name: Build App
        # We require 'sudo' to avoid an error of the existing android sdk. See https://github.com/actions/starter-workflows/issues/58
        run: sudo ./gradlew --full-stacktrace assembleDebug
-    
+
      - name: Utility tests
        # We require 'sudo' to avoid an error of the existing android sdk. See https://github.com/actions/starter-workflows/issues/58
        run:  sudo ./gradlew --full-stacktrace :utility:testDebugUnitTest
@@ -81,7 +96,7 @@ jobs:
        with:
          name: utility reports
          path: utility/build/reports
-     
+
      - name: Domain tests
        # We require 'sudo' to avoid an error of the existing android sdk. See https://github.com/actions/starter-workflows/issues/58
        run:  sudo ./gradlew --full-stacktrace :domain:testDebugUnitTest
@@ -101,26 +116,26 @@ jobs:
        with:
          name: testing reports
          path: testing/build/reports
-  
+
   app_tests:
     name: Robolectric Tests - App Module (Non-Flaky)
     runs-on:  ${{ matrix.os }}
     strategy:
       matrix:
         os: [ubuntu-18.04]
-    steps: 
+    steps:
       - uses: actions/checkout@v2
-      
+
       - uses: actions/cache@v2
         with:
          path: ~/.gradle/caches
          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*') }}-jars-{{ checksum "build.gradle" }}
-         
+
       - name: Set up JDK 1.9
         uses: actions/setup-java@v1
         with:
           java-version: 1.9
-      
+
       - name: Robolectric tests - App Module
         # We require 'sudo' to avoid an error of the existing android sdk. See https://github.com/actions/starter-workflows/issues/58
         run: |

app/src/main/java/org/oppia/android/app/databinding/DrawableBindingAdapters.java

@@ -21,6 +21,7 @@ public static void setBackgroundDrawable(@NonNull View view, @ColorInt int color
     background.setColor(0xff000000 | colorRgb);
   }
 
+  /** Used to set a top rounded-rect background drawable with a data-bound color. */
   @BindingAdapter("app:topRoundedRectDrawableWithColor")
   public static void setTopBackgroundDrawable(@NonNull View view, @ColorInt int colorRgb) {
     view.setBackgroundResource(R.drawable.top_rounded_rect_background);
@@ -29,6 +30,7 @@ public static void setTopBackgroundDrawable(@NonNull View view, @ColorInt int co
     background.setColor(0xff000000 | colorRgb);
   }
 
+  /** Used to set a bottom rounded-rect background drawable with a data-bound color. */
   @BindingAdapter("app:bottomRoundedRectDrawableWithColor")
   public static void setBottomBackgroundDrawable(@NonNull View view, @ColorInt int colorRgb) {
     view.setBackgroundResource(R.drawable.bottom_rounded_rect_background);
@@ -37,6 +39,7 @@ public static void setBottomBackgroundDrawable(@NonNull View view, @ColorInt int
     background.setColor(0xff000000 | colorRgb);
   }
 
+  /** Used to set a rectangular background drawable with a data-bound color. */
   @BindingAdapter("app:rectangleDrawableWithColor")
   public static void setRectangleBackgroundDrawable(@NonNull View view, @ColorInt int colorRgb) {
     view.setBackgroundResource(R.drawable.rectangle_background);
@@ -45,6 +48,7 @@ public static void setRectangleBackgroundDrawable(@NonNull View view, @ColorInt
     background.setColor(0xff000000 | colorRgb);
   }
 
+  /** Used to set a resource background to a button. */
   @BindingAdapter("android:button")
   public static void setBackgroundResource(@NonNull Button button, @DrawableRes int resource) {
     button.setBackgroundResource(resource);

app/src/main/java/org/oppia/android/app/databinding/EditTextBindingAdapters.java

@@ -8,7 +8,7 @@
 /** Holds all custom binding adapters that bind to [EditText]. */
 public final class EditTextBindingAdapters {
 
-  /** Binding adapter for setting a [TextWatcher] as a change listener for an [EditText] */
+  /** Binding adapter for setting a [TextWatcher] as a change listener for an [EditText]. */
   @BindingAdapter("app:textChangedListener")
   public static void bindTextWatcher(@NonNull EditText editText, TextWatcher textWatcher) {
     editText.addTextChangedListener(textWatcher);

app/src/main/java/org/oppia/android/app/databinding/ImageViewBindingAdapters.java

@@ -45,7 +45,7 @@ public static void setImageDrawable(
 
   /**
    * Binds the specified [LessonThumbnailGraphic] as the source for the [ImageView].
-   *
+   * <p/>
    * The view should be specified to have no width/height (when sized in a constraint layout), and
    * use centerCrop for the image to appear correctly.
    */
@@ -58,42 +58,61 @@ public static void setImageDrawable(
     switch (thumbnailGraphic) {
       case BAKER:
         drawableResourceId = R.drawable.lesson_thumbnail_graphic_baker;
+        break;
       case CHILD_WITH_BOOK:
         drawableResourceId = R.drawable.lesson_thumbnail_graphic_child_with_book;
+        break;
       case CHILD_WITH_CUPCAKES:
         drawableResourceId = R.drawable.lesson_thumbnail_graphic_child_with_cupcakes;
+        break;
       case CHILD_WITH_FRACTIONS_HOMEWORK:
         drawableResourceId = R.drawable.lesson_thumbnail_graphic_child_with_fractions_homework;
+        break;
       case DUCK_AND_CHICKEN:
         drawableResourceId = R.drawable.lesson_thumbnail_graphic_duck_and_chicken;
+        break;
       case PERSON_WITH_PIE_CHART:
         drawableResourceId = R.drawable.lesson_thumbnail_graphic_person_with_pie_chart;
+        break;
       case IDENTIFYING_THE_PARTS_OF_A_FRACTION:
         drawableResourceId = R.drawable.topic_fractions_01;
+        break;
       case WRITING_FRACTIONS:
         drawableResourceId = R.drawable.topic_fractions_02;
+        break;
       case EQUIVALENT_FRACTIONS:
         drawableResourceId = R.drawable.topic_fractions_03;
+        break;
       case MIXED_NUMBERS_AND_IMPROPER_FRACTIONS:
         drawableResourceId = R.drawable.topic_fractions_04;
+        break;
       case COMPARING_FRACTIONS:
         drawableResourceId = R.drawable.topic_fractions_05;
+        break;
       case ADDING_AND_SUBTRACTING_FRACTIONS:
         drawableResourceId = R.drawable.topic_fractions_06;
+        break;
       case MULTIPLYING_FRACTIONS:
         drawableResourceId = R.drawable.topic_fractions_07;
+        break;
       case DIVIDING_FRACTIONS:
         drawableResourceId = R.drawable.topic_fractions_08;
+        break;
       case DERIVE_A_RATIO:
         drawableResourceId = R.drawable.topic_ratios_01;
+        break;
       case WHAT_IS_A_FRACTION:
         drawableResourceId = R.drawable.topic_fractions_01;
+        break;
       case FRACTION_OF_A_GROUP:
         drawableResourceId = R.drawable.topic_fractions_02;
+        break;
       case ADDING_FRACTIONS:
         drawableResourceId = R.drawable.topic_fractions_03;
+        break;
       case MIXED_NUMBERS:
         drawableResourceId = R.drawable.topic_fractions_04;
+        break;
       default:
         drawableResourceId = R.drawable.topic_fractions_01;
     }

app/src/main/java/org/oppia/android/app/databinding/TextViewBindingAdapters.java

@@ -6,10 +6,10 @@
 import androidx.annotation.NonNull;
 import androidx.annotation.PluralsRes;
 import androidx.databinding.BindingAdapter;
-import org.oppia.android.R;
-import org.oppia.android.util.system.OppiaDateTimeFormatter;
 import java.util.Locale;
 import java.util.concurrent.TimeUnit;
+import org.oppia.android.R;
+import org.oppia.android.util.system.OppiaDateTimeFormatter;
 
 /** Holds all custom binding adapters that bind to [TextView]. */
 public final class TextViewBindingAdapters {
@@ -29,6 +29,7 @@ public static void setProfileDataText(@NonNull TextView textView, long timestamp
     ));
   }
 
+  /** Binds last used with relative timestamp. */
   @BindingAdapter("profile:lastVisited")
   public static void setProfileLastVisitedText(@NonNull TextView textView, long timestamp) {
     String profileLastUsed = textView.getContext().getString(R.string.profile_last_used);

app/src/main/java/org/oppia/android/app/databinding/ViewBindingAdapters.java

@@ -21,6 +21,9 @@ public static void setLayoutHeight(@NonNull View view, float height) {
     view.setLayoutParams(layoutParams);
   }
 
+  /**
+   * BindingAdapter to set Rotation Animation and Rotation Angle.
+   */
   @BindingAdapter(
       value = {
           "app:isRotationAnimationClockwise",

app/src/test/java/DataBinderMapperImpl.java

@@ -1,13 +1,15 @@
 package androidx.databinding;
+
 // TODO(#1683): Remove when android_local_test works with data-binding.
 /**
  * Generated code necessary to run tests with Bazel.
- *
+ * <p/>
  * Typically, this code is generated by Bazel and included in the srcs list when running tests.
  * However, the `enable_data_binding` flag somehow affects this process. For now, this file must be
  * included in the srcs list of any Bazel test in app module.
  */
 public final class DataBinderMapperImpl extends MergedDataBinderMapper {
+
   DataBinderMapperImpl() {
     addMapper(new org.oppia.android.app.test.DataBinderMapperImpl());
   }