[java] UnusedImports false positive for static import

Fixes #925

docs/pages/release_notes.md

@@ -37,6 +37,7 @@ This is a minor release.
     *   [#920](https://github.com/pmd/pmd/pull/920): \[java] Update valid identifiers in grammar
 *   java-bestpractices
     *   [#784](https://github.com/pmd/pmd/issues/784): \[java] ForLoopCanBeForeach false-positive
+    *   [#925](https://github.com/pmd/pmd/issues/925): \[java] UnusedImports false positive for static import
 *   java-design
     *   [#855](https://github.com/pmd/pmd/issues/855): \[java] ImmutableField false-positive with lambdas
 *   java-documentation

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/ImportWrapper.java

@@ -6,6 +6,7 @@ package net.sourceforge.pmd.lang.rule;
 
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
 import java.util.HashSet;
 import java.util.Set;
 
@@ -35,6 +36,13 @@ public class ImportWrapper {
             for (Field f : type.getFields()) {
                 allDemands.add(f.getName());
             }
+            // also consider static fields, that are not public
+            int requiredMod = Modifier.STATIC;
+            for (Field f : type.getDeclaredFields()) {
+                if ((f.getModifiers() & requiredMod) == requiredMod) {
+                    allDemands.add(f.getName());
+                }
+            }
         }
     }
 

pmd-java/src/test/java/net/sourceforge/pmd/lang/java/rule/bestpractices/unusedimports/ClassWithConstants.java

@@ -0,0 +1,18 @@
+/**
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.java.rule.bestpractices.unusedimports;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class ClassWithConstants {
+
+    private ClassWithConstants() {
+        // Utility class
+    }
+
+    /*package*/ static final List<String> LIST1 = Arrays.asList("A");
+    /*package*/ static final List<String> LIST2 = Arrays.asList("B");
+}

pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/bestpractices/xml/UnusedImports.xml

@@ -395,4 +395,21 @@ public class Foo {
         ]]></code>
     </test-code>
 
+    <test-code>
+        <description>#925 [java] UnusedImports false positive for static import</description>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+package net.sourceforge.pmd.lang.java.rule.bestpractices.unusedimports;
+
+import static net.sourceforge.pmd.lang.java.rule.bestpractices.unusedimports.ClassWithConstants.*;
+
+public class ClassWithImport {
+
+    public static void main(String[] args) {
+        System.out.println("List 1: " + LIST1);
+        System.out.println("List 2: " + LIST2);
+    }
+}
+        ]]></code>
+    </test-code>
 </test-data>