Merge branch 'bug-177'

Fixes #177

pmd-java/src/main/java/net/sourceforge/pmd/lang/java/rule/design/SingularFieldRule.java

@@ -14,6 +14,7 @@ import net.sourceforge.pmd.lang.java.ast.ASTConstructorDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTFieldDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTIfStatement;
 import net.sourceforge.pmd.lang.java.ast.ASTInitializer;
+import net.sourceforge.pmd.lang.java.ast.ASTLambdaExpression;
 import net.sourceforge.pmd.lang.java.ast.ASTMethodDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTPrimaryExpression;
 import net.sourceforge.pmd.lang.java.ast.ASTStatementExpression;
@@ -119,6 +120,12 @@ public class SingularFieldRule extends AbstractLombokAwareRule {
                         break; // Optimization
                     }
 
+                    if (location.getFirstParentOfType(ASTLambdaExpression.class) != null) {
+                        // This usage is inside a lambda expression
+                        violation = false;
+                        break; // Optimization
+                    }
+
                     Node method = location.getFirstParentOfType(ASTMethodDeclaration.class);
                     if (method == null) {
                         method = location.getFirstParentOfType(ASTConstructorDeclaration.class);

pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/design/xml/SingularField.xml

@@ -569,4 +569,40 @@ public class MyClass {
 }
         ]]></code>
     </test-code>
+
+
+    <test-code>
+        <description>#177 [java] SingularField with lambdas as final fields</description>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+/** Dummy class. */
+public final class Test {
+  private Timer timer1;
+  private Timer timer2;
+
+  /** Dummy constructor. */
+  public Timer() {
+    this.timer1 = new Timer(0, e -> {
+      // do nothing for now
+    });
+    this.timer2 = new Timer(0, e -> {
+      // do nothing for now
+    });
+  }
+
+  /** Use a lambda expression to reference timer1 -- triggers SingularField error. */
+  private final Runnable play1 = () -> {
+    this.timer1.start();
+  };
+
+  /** Use an anonymous class to reference timer2 -- no error. */
+  private final Runnable play2 = new Runnable() {
+    @Override
+    public void run() {
+      this.timer2.start();
+    }
+  };
+}
+        ]]></code>
+    </test-code>
 </test-data>

src/site/markdown/overview/changelog.md

@@ -223,6 +223,7 @@ to avoid XSS attacks.
 *   java-design
     *   [#1512](https://sourceforge.net/p/pmd/bugs/1512/): \[java] Combine rules AvoidConstantsInInterface and ConstantsInInterface
     *   [#1552](https://sourceforge.net/p/pmd/bugs/1552/): \[java] MissingBreakInSwitch - False positive for continue
+    *   [#177](https://github.com/pmd/pmd/issues/177): \[java] SingularField with lambdas as final fields
 *   java-imports
     *   [#1546](https://sourceforge.net/p/pmd/bugs/1546/): \[java] UnnecessaryFullyQualifiedNameRule doesn't take into consideration conflict resolution
     *   [#1547](https://sourceforge.net/p/pmd/bugs/1547/): \[java] UnusedImportRule - False Positive for only usage in Javadoc - {@link ClassName#CONSTANT}