fix issue when timestamp is wrongly printed when just a line follow u…

…p should be printed

app/src/processing/app/AbstractTextMonitor.java

@@ -13,6 +13,7 @@
 import java.text.SimpleDateFormat;
 import java.util.Date;
 import java.util.StringTokenizer;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import javax.swing.Box;
 import javax.swing.BoxLayout;
@@ -181,6 +182,7 @@ public void message(final String msg) {
   static class UpdateTextAreaAction implements Runnable {
 
     private static final String LINE_SEPARATOR = "\n";
+    private static AtomicBoolean isStartingLine = new AtomicBoolean(true);
 
     private String msg;
     private boolean addTimeStamp;
@@ -209,16 +211,15 @@ public void run() {
     private String addTimestamps(String text) {
       String now = new SimpleDateFormat("HH:mm:ss.SSS -> ").format(new Date());
       final StringBuilder sb = new StringBuilder(text.length() + now.length());
-      boolean isStartingLine = true;
       StringTokenizer tokenizer = new StringTokenizer(text, LINE_SEPARATOR, true);
       while (tokenizer.hasMoreTokens()) {
-        if (isStartingLine) {
+        if (isStartingLine.get()) {
           sb.append(now);
         }
         String token = tokenizer.nextToken();
         sb.append(token);
         // tokenizer returns "\n" as a single token
-        isStartingLine = token.equals(LINE_SEPARATOR);
+        isStartingLine.set(token.equals(LINE_SEPARATOR));
       }
       return sb.toString();
     }

app/test/processing/app/UpdateTextAreaActionTest.java

@@ -16,6 +16,7 @@ public class UpdateTextAreaActionTest {
   @Before public void setUp() {
     textAreaFIFO = mock(TextAreaFIFO.class);
     text = ArgumentCaptor.forClass(String.class);
+    sendNewLineInOrderToHaveCleanTestStart();
   }
 
   @Test
@@ -64,4 +65,36 @@ public void emptyLinesHaveTimestampToo() {
                                         + TIMESTAMP_REGEX + " -> line_2");
   }
 
+  @Test
+  public void newLinesAreRememberedWhenNewBufferIsUsed() {
+    // given #1
+    AbstractTextMonitor.UpdateTextAreaAction action;
+    action = new AbstractTextMonitor.UpdateTextAreaAction(
+        textAreaFIFO, true, false, "first line without newline");
+
+    // when #1
+    action.run();
+
+    //then #1
+    verify(textAreaFIFO, atLeastOnce()).append(text.capture());
+    assertThat(text.getValue()).matches(TIMESTAMP_REGEX + " -> first line without newline");
+
+    // given #2
+    action = new AbstractTextMonitor.UpdateTextAreaAction(
+        textAreaFIFO, true, false, "more text for first line");
+
+    // when #2
+    action.run();
+
+    //then #2
+    verify(textAreaFIFO, atLeastOnce()).append(text.capture());
+    assertThat(text.getValue()).matches("more text for first line");
+  }
+
+
+  private void sendNewLineInOrderToHaveCleanTestStart() {
+    AbstractTextMonitor.UpdateTextAreaAction action = new AbstractTextMonitor.UpdateTextAreaAction(
+        textAreaFIFO, true, false, "\n");
+    action.run();
+  }
 }