Some utility methods + tests

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/NotificationUtils.java

@@ -19,6 +19,7 @@ package nodomain.freeyourgadget.gadgetbridge.util;
 import android.content.Context;
 import android.support.annotation.NonNull;
 
+import nodomain.freeyourgadget.gadgetbridge.R;
 import nodomain.freeyourgadget.gadgetbridge.model.CallSpec;
 import nodomain.freeyourgadget.gadgetbridge.model.NotificationSpec;
 
@@ -47,13 +48,22 @@ public class NotificationUtils {
     }
 
     @NonNull
-    public static String formatText(String sender, String subject, String body, int lengthBody, int lengthSubject, Context context) {
-        StringBuilder builder = new StringBuilder();
-        builder.append(StringUtils.truncate(body, lengthBody));
-        builder.append(StringUtils.truncate(subject, lengthSubject));
-        builder.append(StringUtils.formatSender(sender, context));
+    public static String formatSender(String sender, Context context) {
+        if (sender == null || sender.length() == 0) {
+            return "";
+        }
+        return context.getString(R.string.StringUtils_sender, sender);
+    }
 
-        return builder.toString();
+
+    @NonNull
+    public static String formatText(String sender, String subject, String body, int lengthBody, int lengthSubject, Context context) {
+        String fBody = StringUtils.truncate(body, lengthBody);
+        String fSubject = StringUtils.truncate(subject, lengthSubject);
+        String fSender = formatSender(sender, context);
+
+        StringBuilder builder = StringUtils.join(" ", fBody, fSubject, fSender);
+        return builder.toString().trim();
     }
 
     public static String getPreferredTextFor(CallSpec callSpec) {

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/StringUtils.java

@@ -16,11 +16,8 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>. */
 package nodomain.freeyourgadget.gadgetbridge.util;
 
-import android.content.Context;
 import android.support.annotation.NonNull;
 
-import nodomain.freeyourgadget.gadgetbridge.R;
-
 public class StringUtils {
 
     public static String truncate(String s, int maxLength){
@@ -47,12 +44,31 @@ public class StringUtils {
         return s;
     }
 
+    /**
+     * Joins the given elements and adds a separator between each element in the resulting string.
+     * There will be no separator at the start or end of the string. There will be no consecutive
+     * separators (even in case an element is null or empty).
+     * @param separator the separator string
+     * @param elements the elements to concatenate to a new string
+     * @return the joined strings, separated by the separator
+     */
     @NonNull
-    public static String formatSender(String sender, Context context) {
-        if (sender == null || sender.length() == 0) {
-            return "";
+    public static StringBuilder join(String separator, String... elements) {
+        StringBuilder builder = new StringBuilder();
+        if (elements == null) {
+            return builder;
         }
-        return context.getString(R.string.StringUtils_sender, sender);
+        boolean hasAdded = false;
+        for (String element : elements) {
+            if (element != null && element.length() > 0) {
+                if (hasAdded) {
+                    builder.append(separator);
+                }
+                builder.append(element);
+                hasAdded = true;
+            }
+        }
+        return builder;
     }
 
     @NonNull

app/src/test/java/nodomain/freeyourgadget/gadgetbridge/test/StringUtilsTest.java

@@ -0,0 +1,56 @@
+package nodomain.freeyourgadget.gadgetbridge.test;
+
+import org.junit.Test;
+
+import nodomain.freeyourgadget.gadgetbridge.util.StringUtils;
+
+import static org.junit.Assert.assertEquals;
+
+public class StringUtilsTest extends TestBase {
+    private static final String SEP = ":";
+    private static final String E1 = "e1";
+    private static final String E2 = "e2";
+    private static final String E3 = "e3";
+
+    @Test
+    public void testJoinNull() {
+        StringBuilder result = StringUtils.join(SEP, (String[]) null);
+        assertEquals("", result.toString());
+    }
+
+    @Test
+    public void testJoinNullElement() {
+        StringBuilder result = StringUtils.join(SEP, (String) null);
+        assertEquals("", result.toString());
+    }
+
+    @Test
+    public void testJoinSingleElement() {
+        StringBuilder result = StringUtils.join(SEP, E1);
+        assertEquals(E1, result.toString());
+    }
+
+    @Test
+    public void testJoinSingleAndNullElement() {
+        StringBuilder result = StringUtils.join(SEP, E1, null);
+        assertEquals(E1, result.toString());
+    }
+
+    @Test
+    public void testJoinTwoElements() {
+        StringBuilder result = StringUtils.join(SEP, E1, E2);
+        assertEquals(E1 + SEP + E2, result.toString());
+    }
+
+    @Test
+    public void testJoinTwoElementsAndNull() {
+        StringBuilder result = StringUtils.join(SEP, E1, null, E2);
+        assertEquals(E1 + SEP + E2, result.toString());
+    }
+
+    @Test
+    public void testJoinThreeElements() {
+        StringBuilder result = StringUtils.join(SEP, E1, E2, E3);
+        assertEquals(E1 + SEP + E2 + SEP + E3, result.toString());
+    }
+}