Empty Line Separator Check, fixed Exception if file doesn't have header, issue #621

src/main/java/com/puppycrawl/tools/checkstyle/checks/whitespace/EmptyLineSeparatorCheck.java

@@ -285,11 +285,15 @@ public class EmptyLineSeparatorCheck extends Check
      */
     private boolean isPrePreviousLineEmpty(DetailAST token)
     {
+        boolean result = false;
         final int lineNo = token.getLineNo();
         // 3 is the number of the pre-previous line because the numbering starts from zero.
         final int number = 3;
-        final String prePreviousLine = getLines()[lineNo - number];
-        return prePreviousLine.trim().isEmpty();
+        if (lineNo >= number) {
+            final String prePreviousLine = getLines()[lineNo - number];
+            result = prePreviousLine.trim().isEmpty();
+        }
+        return result;
     }
 
     /**

src/test/java/com/puppycrawl/tools/checkstyle/checks/whitespace/EmptyLineSeparatorCheckTest.java

@@ -81,4 +81,15 @@ public class EmptyLineSeparatorCheckTest
         };
         verify(checkConfig, getPath("whitespace/InputEmptyLineSeparatorCheckMultipleEmptyLines.java"), expected);
     }
+
+    @Test
+    public void testFormerArrayIndexOutOfBounds() throws Exception
+    {
+        DefaultConfiguration checkConfig = createCheckConfig(EmptyLineSeparatorCheck.class);
+        checkConfig.addAttribute("allowMultipleEmptyLines", "false");
+        final String[] expected = {
+
+        };
+        verify(checkConfig, getPath("whitespace/InputEmptyLineSeparatorFormerException.java"), expected);
+    }
 }

src/test/resources/com/puppycrawl/tools/checkstyle/whitespace/InputEmptyLineSeparatorFormerException.java

@@ -0,0 +1,6 @@
+package com.puppycrawl.tools.checkstyle.whitespace;
+
+public class InputEmptyLineSeparatorFormerException
+{
+
+}