Empty Line Separator Check, added option for managing empty lines bet…

…ween class members, issue checkstyle#530

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

@@ -106,14 +106,66 @@
  * </module>
  * </pre>
  *
- * @author maxvetrenko
+ * <p>
+ * Example of declarations with multiple empty lines between class members (allowed by default):
+ * </p>
+ *
+ * <pre>
+ * ///////////////////////////////////////////////////
+ * //HEADER
+ * ///////////////////////////////////////////////////
+ *
+ *
+ * package com.puppycrawl.tools.checkstyle.whitespace;
+ *
+ *
+ *
+ * import java.io.Serializable;
  *
+ *
+ * class Foo
+ * {
+ *     public static final int FOO_CONST = 1;
+ *
+ *
+ *
+ *     public void foo() {}
+ * }
+ * </pre>
+ * <p>
+ * An example how to disallow multiple empty lines between class members:
+ * </p>
+ * <pre>
+ * &lt;module name="EmptyLineSeparator"&gt;
+ *    &lt;property name="allowMultipleEmptyLines" value="false"/&gt;
+ * &lt;/module&gt;
+ * </pre>
+ *
+ * @author maxvetrenko
+ * @author <a href="mailto:nesterenko-aleksey@list.ru">Aleksey Nesterenko</a>
  */
 public class EmptyLineSeparatorCheck extends Check
 {
+
+    /**
+     * A key is pointing to the warning message empty.line.separator in "messages.properties"
+     * file.
+     */
+    public static final String MSG_SHOULD_BE_SEPARATED = "empty.line.separator";
+
+    /**
+     * A key is pointing to the warning message empty.line.separator.multiple.lines
+     *  in "messages.properties"
+     * file.
+     */
+    public static final String MSG_MULTIPLE_LINES = "empty.line.separator.multiple.lines";
+
     /** */
     private boolean allowNoEmptyLineBetweenFields;
 
+    /** Allows multiple empty lines between class members. */
+    private boolean allowMultipleEmptyLines = true;
+
     /**
      * Allow no empty line between fields.
      * @param allow
@@ -124,6 +176,15 @@ public final void setAllowNoEmptyLineBetweenFields(boolean allow)
         allowNoEmptyLineBetweenFields = allow;
     }
 
+    /**
+     * Allow multiple empty lines between class members.
+     * @param allow User's value.
+     */
+    public void setAllowMultipleEmptyLines(boolean allow)
+    {
+        allowMultipleEmptyLines = allow;
+    }
+
     @Override
     public int[] getDefaultTokens()
     {
@@ -146,43 +207,69 @@ public void visitToken(DetailAST ast)
     {
         final DetailAST nextToken = ast.getNextSibling();
 
-        if (nextToken != null && nextToken.getType() != TokenTypes.RCURLY) {
+        if (nextToken != null) {
             final int astType = ast.getType();
             switch (astType) {
                 case TokenTypes.VARIABLE_DEF:
                     if (isTypeField(ast) && !hasEmptyLineAfter(ast)) {
                         if (allowNoEmptyLineBetweenFields
                             && nextToken.getType() != TokenTypes.VARIABLE_DEF)
                         {
-                            log(nextToken.getLineNo(), "empty.line.separator",
+                            log(nextToken.getLineNo(), MSG_SHOULD_BE_SEPARATED,
                                  nextToken.getText());
                         }
-                        else if (!allowNoEmptyLineBetweenFields) {
-                            log(nextToken.getLineNo(), "empty.line.separator",
+                        else if (!allowNoEmptyLineBetweenFields || !allowMultipleEmptyLines) {
+                            log(nextToken.getLineNo(), MSG_SHOULD_BE_SEPARATED,
                                  nextToken.getText());
                         }
                     }
+                    if (!allowMultipleEmptyLines && isTypeField(ast) && hasEmptyLinesBefore(ast)) {
+                        log(ast.getLineNo(), MSG_MULTIPLE_LINES, ast.getText());
+                    }
                     break;
                 case TokenTypes.IMPORT:
                     if (astType != nextToken.getType() && !hasEmptyLineAfter(ast)
                         || (ast.getLineNo() > 1 && !hasEmptyLineBefore(ast)
                             && ast.getPreviousSibling() == null))
                     {
-                        log(nextToken.getLineNo(), "empty.line.separator", nextToken.getText());
+                        log(nextToken.getLineNo(), MSG_SHOULD_BE_SEPARATED, nextToken.getText());
+                    }
+                    if (!allowMultipleEmptyLines && hasEmptyLinesBefore(ast)) {
+                        log(ast.getLineNo(), MSG_MULTIPLE_LINES, ast.getText());
                     }
                     break;
                 case TokenTypes.PACKAGE_DEF:
                     if (ast.getLineNo() > 1 && !hasEmptyLineBefore(ast)) {
-                        log(ast.getLineNo(), "empty.line.separator", ast.getText());
+                        log(ast.getLineNo(), MSG_SHOULD_BE_SEPARATED, ast.getText());
+                    }
+                    if (!allowMultipleEmptyLines && hasEmptyLinesBefore(ast)) {
+                        log(ast.getLineNo(), MSG_MULTIPLE_LINES, ast.getText());
                     }
                 default:
-                    if (!hasEmptyLineAfter(ast)) {
-                        log(nextToken.getLineNo(), "empty.line.separator", nextToken.getText());
+                    if (nextToken.getType() != TokenTypes.RCURLY && !hasEmptyLineAfter(ast)) {
+                        log(nextToken.getLineNo(), MSG_SHOULD_BE_SEPARATED, nextToken.getText());
+                    }
+                    if (!allowMultipleEmptyLines && hasEmptyLinesBefore(ast)) {
+                        log(ast.getLineNo(), MSG_MULTIPLE_LINES, ast.getText());
                     }
             }
         }
     }
 
+    /**
+     * Checks if a token has more than 1 empty lines before.
+     * @param token DetailAST token.
+     * @return true, if token have empty lines before.
+     */
+    private boolean hasEmptyLinesBefore(DetailAST token)
+    {
+        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 lineBefore = getLines()[lineNo - number];
+        return lineBefore.trim().isEmpty();
+    }
+
     /**
      * Checks if token have empty line after.
      * @param token token.

src/main/resources/com/puppycrawl/tools/checkstyle/checks/whitespace/messages.properties

@@ -1,4 +1,5 @@
 empty.line.separator=''{0}'' should be separated from previous statement.
+empty.line.separator.multiple.lines=''{0}'' has more than 1 empty lines before.
 
 containsTab=Line contains a tab character.
 file.containsTab=File contains tab characters (this is the first instance).

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

@@ -66,4 +66,19 @@ public void testHeader() throws Exception
         };
         verify(checkConfig, getPath("whitespace/InputEmptyLineSeparatorCheckHeader.java"), expected);
     }
+
+    @Test
+    public void testMultipleEmptyLinesBetweenClassMembers() throws Exception
+    {
+        DefaultConfiguration checkConfig = createCheckConfig(EmptyLineSeparatorCheck.class);
+        checkConfig.addAttribute("allowMultipleEmptyLines", "false");
+        final String[] expected = {
+            "21: 'package' has more than 1 empty lines before.",
+            "24: 'import' has more than 1 empty lines before.",
+            "33: 'VARIABLE_DEF' has more than 1 empty lines before.",
+            "38: 'VARIABLE_DEF' has more than 1 empty lines before.",
+            "43: 'METHOD_DEF' has more than 1 empty lines before.",
+        };
+        verify(checkConfig, getPath("whitespace/InputEmptyLineSeparatorCheckMultipleEmptyLines.java"), expected);
+    }
 }

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

@@ -0,0 +1,47 @@
+////////////////////////////////////////////////////////////////////////////////
+// checkstyle: Checks Java source code for adherence to a set of rules.
+// Copyright (C) 2001-2014  Oliver Burn
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+////////////////////////////////////////////////////////////////////////////////
+
+
+package com.puppycrawl.tools.checkstyle.whitespace;
+
+
+import java.util.*;
+
+import java.io.*;
+
+
+public class InputEmptyLineSeparatorCheckMultipleEmptyLines
+{
+
+
+    private int counter;
+
+
+
+
+    private Object obj = null;
+
+    private int k;
+
+
+    private static void foo() {}
+
+    private static void foo1() {}
+
+}

src/xdocs/config_whitespace.xml

@@ -1351,6 +1351,12 @@ import com.puppycrawl.tools.checkstyle.api.Check;
             <th><a href="property_types.html#boolean">boolean</a></th>
             <th>false</th>
           </tr>
+          <tr>
+            <th>allowMultipleEmptyLines</th>
+            <th>Allow multiple empty lines between class members</th>
+            <th><a href="property_types.html#boolean">boolean</a></th>
+            <th><code>true</code></th>
+          </tr>
         </table>
       </subsection>
 
@@ -1411,6 +1417,44 @@ class Foo
       <source>
 &lt;module name="EmptyLineSeparator"&gt;
     &lt;property name="allowNoEmptyLineBetweenFields" value="true"/&gt;
+&lt;/module&gt;
+      </source>
+      <p>
+        Example of declarations with multiple empty lines between class members
+         (allowed by default):
+      </p>
+      <source>
+///////////////////////////////////////////////////
+//HEADER
+///////////////////////////////////////////////////
+
+
+
+package com.puppycrawl.tools.checkstyle.whitespace;
+
+
+
+import java.io.Serializable;
+
+
+
+class Foo
+{
+
+
+    public static final int FOO_CONST = 1;
+
+
+
+
+    public void foo() {} //should be separated from previous statement.
+}
+      <p>
+        An example how to disallow multiple empty lines between class members:
+      </p>
+      <source>
+&lt;module name=&quot;EmptyLineSeparator&quot;&gt;
+    &lt;property name=&quot;allowMultipleEmptyLines&quot; value=&quot;true&quot;/&gt;
 &lt;/module&gt;
       </source>
       </subsection>