minor refactorings and test cases

app/build.gradle.kts

@@ -65,4 +65,5 @@ android {
 dependencies {
     implementation("androidx.appcompat:appcompat:1.4.0")
     implementation("com.google.android.material:material:1.4.0")
+    testImplementation("junit:junit:4.+")
 }

app/src/main/java/org/grapheneos/pdfviewer/GestureHelper.java

@@ -33,23 +33,22 @@ public boolean onSingleTapUp(MotionEvent motionEvent) {
 
         final ScaleGestureDetector scaleDetector = new ScaleGestureDetector(context,
                 new ScaleGestureDetector.SimpleOnScaleGestureListener() {
-                    float SPAN_RATIO = 600;
+                    final float SPAN_RATIO = 600;
                     float initialSpan;
-                    float prevNbStep;
+                    float prevNbStep = 0;
 
                     @Override
                     public boolean onScaleBegin(ScaleGestureDetector detector) {
                         initialSpan = detector.getCurrentSpan();
-                        prevNbStep = 0;
                         return true;
                     }
 
                     @Override
                     public boolean onScale(ScaleGestureDetector detector) {
-                        float spanDiff = initialSpan - detector.getCurrentSpan();
-                        float curNbStep = spanDiff / SPAN_RATIO;
+                        final float spanDiff = initialSpan - detector.getCurrentSpan();
+                        final float curNbStep = spanDiff / SPAN_RATIO;
 
-                        float stepDiff = curNbStep - prevNbStep;
+                        final float stepDiff = curNbStep - prevNbStep;
                         if (stepDiff > 0) {
                             listener.onZoomOut(stepDiff);
                         } else {

app/src/main/java/org/grapheneos/pdfviewer/Utils.java

@@ -10,9 +10,9 @@
 
 public class Utils {
     public static String parseFileSize(long fileSize) {
-        final double kb = fileSize / 1000;
+        final double kb = fileSize / 1000d;
 
-        if (kb == 0) {
+        if (kb == 0d) {
             return fileSize + " Bytes";
         }
 
@@ -39,14 +39,14 @@ public static String parseDate(String date) throws ParseException {
 
         final Calendar calendar = Calendar.getInstance();
         final int currentYear = calendar.get(Calendar.YEAR);
-        int year;
 
         // Year is required
         String field = date.substring(position += 2, 6);
         if (!TextUtils.isDigitsOnly(field)) {
             throw new ParseException("Invalid year", position);
         }
-        year = Integer.valueOf(field);
+
+        int year = Integer.valueOf(field);
         if (year > currentYear) {
             year = currentYear;
         }

app/src/test/kotlin/org/grapheneos/pdfviewer/UtilsTests.kt

@@ -0,0 +1,30 @@
+package org.grapheneos.pdfviewer
+
+import org.junit.Assert
+import org.junit.Test
+
+class UtilsTests {
+    @Test
+    fun `Should parse File Size (kB)`() {
+        val fileSize: Long = 1_000
+        Assert.assertEquals("1 kB (${fileSize} Bytes)", Utils.parseFileSize(fileSize))
+    }
+
+    @Test
+    fun `Should parse File Size (decimal kB)`() {
+        val fileSize: Long = 1_024
+        Assert.assertEquals("1,03 kB (${fileSize} Bytes)", Utils.parseFileSize(fileSize))
+    }
+
+    @Test
+    fun `Should parse File Size (MB)`() {
+        val fileSize: Long = 1_000_000
+        Assert.assertEquals("1 MB (${fileSize} Bytes)", Utils.parseFileSize(fileSize))
+    }
+
+    @Test
+    fun `Should parse File Size (decimal MB)`() {
+        val fileSize: Long = 1_240_000
+        Assert.assertEquals("1,24 MB (${fileSize} Bytes)", Utils.parseFileSize(fileSize))
+    }
+}