#1345 UseCollectionIsEmpty throws NullPointerException

pmd-java/src/main/java/net/sourceforge/pmd/lang/java/rule/AbstractInefficientZeroCheck.java

@@ -104,14 +104,32 @@ public abstract class AbstractInefficientZeroCheck extends AbstractJavaRule {
     private boolean isCompare(Node equality) {
         if (isLiteralLeftHand(equality)) {
             return checkComparison(inverse.get(equality.getImage()), equality, 0);
-        } else {
+        } else if (isLiteralRightHand(equality)) {
             return checkComparison(equality.getImage(), equality, 1);
         }
+        return false;
     }
 
     private boolean isLiteralLeftHand(Node equality) {
-        return equality.jjtGetChild(0).jjtGetChild(0).jjtGetNumChildren() > 0
-                && equality.jjtGetChild(0).jjtGetChild(0).jjtGetChild(0) instanceof ASTLiteral;
+        return isLiteral(equality, 0);
+    }
+
+    private boolean isLiteralRightHand(Node equality) {
+        return isLiteral(equality, 1);
+    }
+
+    private boolean isLiteral(Node equality, int child) {
+        Node target = equality.jjtGetChild(child);
+        target = getFirstChildOrThis(target);
+        target = getFirstChildOrThis(target);
+        return target instanceof ASTLiteral;
+    }
+
+    private Node getFirstChildOrThis(Node node) {
+        if (node.jjtGetNumChildren() > 0) {
+            return node.jjtGetChild(0);
+        }
+        return node;
     }
 
     /**
@@ -126,7 +144,10 @@ public abstract class AbstractInefficientZeroCheck extends AbstractJavaRule {
      * @see #getComparisonTargets()
      */
     private boolean checkComparison(String operator, Node equality, int i) {
-        Node target = equality.jjtGetChild(i).jjtGetChild(0).jjtGetChild(0);
+        Node target = equality
+                .jjtGetChild(i)
+                .jjtGetChild(0)
+                .jjtGetChild(0);
         return target instanceof ASTLiteral && getComparisonTargets().get(operator).contains(target.getImage());
     }
 

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

@@ -291,6 +291,29 @@ public class PMDIsEmptyFalsePositive {
             // do something
         }
     }
+}
+        ]]></code>
+    </test-code>
+    <test-code>
+        <description>#1345 UseCollectionIsEmpty throws NullPointerException</description>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+package org.oikarinen.pmdbugbait;
+import java.util.List;
+
+public class PmdBugBait {
+    public int getSize() {
+        return 0;
+    }
+
+    /**
+     * "this." before the method call triggers the bug
+     */
+    public void compareSizeToThisPointMethod(List<String> list) {
+        if (list.size() < this.getSize()) {
+            throw new IllegalArgumentException();
+        }
+    }
 }
         ]]></code>
     </test-code>

src/site/markdown/overview/changelog.md

@@ -14,5 +14,6 @@
 
 *   [#1335](https://sourceforge.net/p/pmd/bugs/1335/): GuardLogStatementJavaUtil should not apply to SLF4J Logger
 *   [#1342](https://sourceforge.net/p/pmd/bugs/1342/): UseConcurrentHashMap false positive (with documentation example)
+*   [#1345](https://sourceforge.net/p/pmd/bugs/1345/): UseCollectionIsEmpty throws NullPointerException
 
 **API Changes:**