[java] SwitchDensity: Fix FP with default label

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

@@ -7,6 +7,7 @@ package net.sourceforge.pmd.lang.java.rule.design;
 import static net.sourceforge.pmd.properties.constraints.NumericConstraints.positive;
 
 import net.sourceforge.pmd.lang.java.ast.ASTStatement;
+import net.sourceforge.pmd.lang.java.ast.ASTSwitchBranch;
 import net.sourceforge.pmd.lang.java.ast.ASTSwitchExpression;
 import net.sourceforge.pmd.lang.java.ast.ASTSwitchLike;
 import net.sourceforge.pmd.lang.java.ast.ASTSwitchStatement;
@@ -53,7 +54,9 @@ public class SwitchDensityRule extends AbstractJavaRulechainRule {
     public Void visitSwitchLike(ASTSwitchLike node, Object data) {
         // note: this does not cross find boundaries.
         int stmtCount = node.descendants(ASTStatement.class).count();
-        int labelCount = node.getBranches().sumBy(branch -> branch.getLabel().getExprList().count());
+        int labelCount = node.getBranches()
+                .map(ASTSwitchBranch::getLabel)
+                .sumBy(label -> label.isDefault() ? 1 : label.getExprList().count());
 
         // note: if labelCount is zero, double division will produce NaN, not ArithmeticException
         double density = stmtCount / (double) labelCount;

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

@@ -113,6 +113,28 @@ public class SwitchDensity3 {
             }
         }
     }
+}
+        ]]></code>
+    </test-code>
+    
+    <test-code>
+        <description>False positive with default label</description>
+        <rule-property name="minimum">10</rule-property>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+public class SwitchWithDefault
+{
+    public void someMethod()
+    {
+        int i = 0;
+        switch (i)
+        {
+            default:
+                i--;
+                i++;
+                break;
+        }
+    }
 }
         ]]></code>
     </test-code>