fix for bug 1560940: MultipleStringLiteralCheck now ignores annotations by default. It is possible to retain the old behaviour by setting the new check property ignoreOccurrenceContext to an empty value.

src/checkstyle/com/puppycrawl/tools/checkstyle/checks/coding/MultipleStringLiteralsCheck.java

@@ -19,6 +19,7 @@
 package com.puppycrawl.tools.checkstyle.checks.coding;
 
 import java.util.ArrayList;
+import java.util.BitSet;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Set;
@@ -42,6 +43,12 @@ public class MultipleStringLiteralsCheck extends Check
      * <String, ArrayList>, with the ArrayList containing StringInfo objects.
      */
     private final HashMap mStringMap = new HashMap();
+
+    /**
+     * Marks the TokenTypes where duplicate strings should be ignored.
+     */
+    private final BitSet mIgnoreOccurrenceContext = new BitSet();
+
     /**
      * The allowed number of string duplicates in a file before an error is
      * generated.
@@ -68,6 +75,7 @@ public class MultipleStringLiteralsCheck extends Check
     public MultipleStringLiteralsCheck()
     {
         setIgnoreStringsRegexp("^\"\"$");
+        mIgnoreOccurrenceContext.set(TokenTypes.ANNOTATION);
     }
 
     /**
@@ -86,6 +94,20 @@ public class MultipleStringLiteralsCheck extends Check
         }
     }
 
+    /**
+     * Adds a set of tokens the check is interested in.
+     * @param aStrRep the string representation of the tokens interested in
+     */
+    public final void setIgnoreOccurrenceContext(String[] aStrRep)
+    {
+        mIgnoreOccurrenceContext.clear();
+        for (int i = 0; i < aStrRep.length; i++) {
+            final String s = aStrRep[i];
+            final int type = TokenTypes.getTokenId(s);
+            mIgnoreOccurrenceContext.set(type);
+        }
+    }
+
     /** {@inheritDoc} */
     public int[] getDefaultTokens()
     {
@@ -95,6 +117,9 @@ public class MultipleStringLiteralsCheck extends Check
     /** {@inheritDoc} */
     public void visitToken(DetailAST aAST)
     {
+        if (isInIgnoreOccurrenceContext(aAST)) {
+            return;
+        }
         final String currentString = aAST.getText();
         if ((mPattern == null) || !mPattern.matcher(currentString).find()) {
             ArrayList hitList = (ArrayList) mStringMap.get(currentString);
@@ -108,6 +133,28 @@ public class MultipleStringLiteralsCheck extends Check
         }
     }
 
+    /**
+     * Analyses the path from the AST root to a given AST for occurrences
+     * of the token types in {@link #mIgnoreOccurrenceContext}.
+     *
+     * @param aAST the node from where to start searching towards the root node
+     * @return whether the path from the root node to aAST contains one of the
+     * token type in {@link #mIgnoreOccurrenceContext}.
+     */
+    private boolean isInIgnoreOccurrenceContext(DetailAST aAST)
+    {
+        for (DetailAST token = aAST;
+             token.getParent() != null;
+             token = token.getParent())
+        {
+            final int type = token.getType();
+            if (mIgnoreOccurrenceContext.get(type)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     /** {@inheritDoc} */
     public void beginTree(DetailAST aRootAST)
     {

src/testinputs/com/puppycrawl/tools/checkstyle/coding/InputMultipleStringLiterals.java

@@ -15,4 +15,16 @@ public class InputMultipleStringLiterals
         // The following is not reported, since it is two string literals.
         String a2 = "String" + "Contents";
     }
+
+    @SuppressWarnings("unchecked")
+    void method2(){}
+
+    @SuppressWarnings("unchecked")
+    void method3(){}
+
+    @SuppressWarnings("unchecked")
+    void method4(){}
+
+    @SuppressWarnings("unchecked")
+    void method5(){}
 }

src/tests/com/puppycrawl/tools/checkstyle/checks/coding/MultipleStringLiteralsCheckTest.java

@@ -56,4 +56,21 @@ public class MultipleStringLiteralsCheckTest extends BaseCheckTestCase
                getPath("coding" + File.separator + "InputMultipleStringLiterals.java"),
                expected);
     }
+
+    public void testItWithoutIgnoringAnnotations() throws Exception
+    {
+        DefaultConfiguration checkConfig =
+            createCheckConfig(MultipleStringLiteralsCheck.class);
+        checkConfig.addAttribute("allowedDuplicates", "3");
+        checkConfig.addAttribute("ignoreOccurrenceContext", "");
+
+        final String[] expected = {
+            "19:23: The String \"unchecked\" appears 4 times in the file.",
+        };
+
+        verify(checkConfig,
+               getPath("coding" + File.separator + "InputMultipleStringLiterals.java"),
+               expected);
+    }
+
 }

src/xdocs/config_coding.xml

@@ -2019,6 +2019,23 @@ case 3:
             <td><a href="property_types.html#regexp">regular expression</a></td>
             <td><span class="default">^""$</span> (ignore empty strings)</td>
           </tr>
+          <tr>
+            <td>ignoreOccurrenceContext</td>
+            <td>
+              Token type names where duplicate strings are ignored even if they don't match
+              ignoredStringsRegexp. This allows you to exclude syntactical contexts like
+              Annotations or static initializers from the check.
+            </td>
+            <td>
+              <a href="property_types.html#stringSet">list</a> of 
+              <a href="api/com/puppycrawl/tools/checkstyle/api/TokenTypes.html">token type</a>
+              names
+            </td>
+            <td>
+              <span class="default">ANNOTATION</span> 
+              (ignore strings inside the context of an annotation)
+            </td>
+          </tr>
         </table>
       </subsection>
 
@@ -2046,6 +2063,17 @@ case 3:
         <source>
 &lt;module name=&quot;MultipleStringLiterals&quot;&gt;
     &lt;property name=&quot;allowedDuplicates&quot; value='^((&quot;&quot;)|(&quot;, &quot;))$'/&gt;
+&lt;/module&gt;
+        </source>
+
+        <p>
+          To configure the check so that it flags duplicate strings in all
+          syntactical contexts, even in annotations like
+          <span class="default">@SuppressWarnings("unchecked")</span>:
+        </p>
+        <source>
+&lt;module name=&quot;MultipleStringLiterals&quot;&gt;
+    &lt;property name=&quot;ignoreOccurrenceContext&quot; value=&quot;&quot;/&gt;
 &lt;/module&gt;
         </source>
       </subsection>

src/xdocs/releasenotes.xml

@@ -16,6 +16,11 @@
         <li>
           checkstyle-all.jar contained some classes from jakarta commons-collections twice. (bug 1630361)
         </li>
+        <li>
+          Multiple string literal check now ignores annotations by default (bug 1560940).
+          It is possible to retain the old behaviour by setting the new check property
+          ignoreOccurrenceContext to an empty value.
+        </li>
       </ul>
 
       <p>New features:</p>