question 2 en anglais

exercises/using-pmd.md

@@ -4,3 +4,33 @@ Pick a Java project from Github (see the [instructions](../sujet.md) for suggest
 
 ## Answer
 
+We clone the project `commons-math`
+https://github.com/apache/commons-math
+We found a problem that it's not worth to change 
+`./commons-math/commons-math-core/src/main/java/org/apache/commons/math4/core/jdkmath/AccurateMath.java:396:	UselessParentheses:	Useless parentheses around `0.5 * t`.`
+And here is the code that PMD a indiqué: 
+```
+            if (x >= LOG_MAX_VALUE) {
+                // Avoid overflow (MATH-905).
+                final double t = exp(0.5 * x);
+                return (0.5 * t) * t;
+```
+
+As we can see the parentheses didn't cause any harm here but it is a true positive
+
+For a false positive, we found this one: 
+`./commons-math/commons-math-legacy-core/src/test/java/org/apache/commons/math4/legacy/core/IntegerSequenceTest.java:255:	UnusedLocalVariable:	Avoid unused local variables such as 'inc'.`
+
+```
+    @Test(expected = ZeroException.class)
+    public void testIncrementZeroStep() {
+        final int step = 0;
+
+        final IntegerSequence.Incrementor inc
+            = IntegerSequence.Incrementor.create()
+            .withIncrement(step);
+    }
+
+```
+
+Because the purpose of the test is to trigger the bug when create object.