new T[0] -> T.EMPTY_ARRAY_FIELD inspection and quick fix

plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/META-INF/InspectionGadgets.xml

@@ -1624,6 +1624,10 @@
                      bundle="com.siyeh.InspectionGadgetsBundle" key="array.allocation.zero.length.display.name"
                      groupBundle="messages.InspectionsBundle" groupKey="group.names.memory.issues" enabledByDefault="false" level="WARNING"
                      implementationClass="com.siyeh.ig.memory.ZeroLengthArrayInitializationInspection"/>
+    <localInspection groupPath="Java" language="JAVA" suppressId="ConstantForZeroLengthArrayAllocation" shortName="UnnecessaryEmptyArrayUsage"
+                     bundle="com.siyeh.InspectionGadgetsBundle" key="constant.for.zero.length.array.display.name"
+                     groupBundle="messages.InspectionsBundle" groupKey="group.names.memory.issues" enabledByDefault="true" level="WARNING"
+                     implementationClass="com.siyeh.ig.memory.UnnecessaryEmptyArrayUsageInspection"/>
 
     <!--group.names.method.metrics-->
     <localInspection groupPath="Java" language="JAVA" suppressId="ConstructorWithTooManyParameters" shortName="ParametersPerConstructor"

plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/InspectionGadgetsBundle.properties

@@ -185,6 +185,10 @@ gc.call.display.name=Calls to 'System.gc()' or 'Runtime.gc()'
 gc.call.problem.descriptor=<code>#ref</code> should not be called in production code #loc
 array.allocation.zero.length.display.name=Zero-length array allocation
 array.allocation.zero.length.problem.descriptor=Allocation of zero length array #loc
+constant.for.zero.length.array.display.name=Unnecessary zero length array usage
+constant.for.zero.length.array.problem.descriptor=Zero length array can be changed to constant #loc
+constant.for.zero.length.array.quickfix.family=Replace with constant
+replace.with=Replace with ''{0}''
 multiple.loggers.display.name=Class with multiple loggers
 logger.name.option=Logger &class name:
 multiple.loggers.problem.descriptor=Class <code>#ref</code> declares multiple loggers #loc

plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/memory/ReplaceEmptyArrayToConstantFix.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2000-2016 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.siyeh.ig.memory;
+
+import com.intellij.codeInspection.ProblemDescriptor;
+import com.intellij.openapi.project.Project;
+import com.intellij.psi.*;
+import com.intellij.psi.codeStyle.JavaCodeStyleManager;
+import com.siyeh.InspectionGadgetsBundle;
+import com.siyeh.ig.InspectionGadgetsFix;
+import org.jetbrains.annotations.Nls;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * @author Konstantin Bulenkov
+ */
+public class ReplaceEmptyArrayToConstantFix extends InspectionGadgetsFix {
+  private final String myText;
+  private final String myName;
+
+  public ReplaceEmptyArrayToConstantFix(PsiClass aClass, PsiField field) {
+    myText = aClass.getQualifiedName() + "." + field.getName();
+    myName = InspectionGadgetsBundle.message("replace.with", aClass.getName() + "." + field.getName());
+  }
+
+  @Nls
+  @NotNull
+  @Override
+  public String getName() {
+    return myName;
+  }
+
+  @Nls
+  @NotNull
+  @Override
+  public String getFamilyName() {
+    return InspectionGadgetsBundle.message("constant.for.zero.length.array.quickfix.family");
+  }
+
+  @Override
+  protected void doFix(Project project, ProblemDescriptor descriptor) {
+    PsiExpression newExp = JavaPsiFacade.getInstance(project).getElementFactory().createExpressionFromText(myText, descriptor.getPsiElement());
+    PsiElement element = descriptor.getPsiElement().replace(newExp);
+    JavaCodeStyleManager.getInstance(project).shortenClassReferences(element);
+  }
+}

plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/memory/UnnecessaryEmptyArrayUsageInspection.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2000-2016 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.siyeh.ig.memory;
+
+import com.intellij.psi.*;
+import com.intellij.psi.util.PsiTreeUtil;
+import com.intellij.psi.util.PsiTypesUtil;
+import com.siyeh.InspectionGadgetsBundle;
+import com.siyeh.ig.BaseInspection;
+import com.siyeh.ig.BaseInspectionVisitor;
+import com.siyeh.ig.InspectionGadgetsFix;
+import com.siyeh.ig.psiutils.ExpressionUtils;
+import org.jetbrains.annotations.Nls;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * @author Konstantin Bulenkov
+ */
+public class UnnecessaryEmptyArrayUsageInspection extends BaseInspection {
+  @Nls
+  @NotNull
+  @Override
+  public String getDisplayName() {
+    return InspectionGadgetsBundle.message("constant.for.zero.length.array.display.name");
+  }
+
+  @NotNull
+  @Override
+  protected String buildErrorString(Object... infos) {
+    return InspectionGadgetsBundle.message("constant.for.zero.length.array.problem.descriptor");
+  }
+
+  @Nullable
+  @Override
+  protected InspectionGadgetsFix buildFix(Object... infos) {
+    return new ReplaceEmptyArrayToConstantFix((PsiClass)infos[0], (PsiField)infos[1]);
+  }
+
+  @Override
+  public BaseInspectionVisitor buildVisitor() {
+    return new BaseInspectionVisitor() {
+      @Override
+      public void visitNewExpression(PsiNewExpression expression) {
+        if (ExpressionUtils.isZeroLengthArrayConstruction(expression)) {
+          PsiType type = expression.getType();
+          if (type instanceof PsiArrayType) {
+            PsiType arrayType = ((PsiArrayType)type).getComponentType();
+            PsiClass typeClass = PsiTypesUtil.getPsiClass(arrayType);
+            if (typeClass != null) {
+              for (PsiField field : typeClass.getFields()) {
+                PsiModifierList modifiers = field.getModifierList();
+                if (modifiers != null
+                    && !typeClass.isEquivalentTo(PsiTreeUtil.findFirstParent(expression, (e) -> e instanceof PsiClass))
+                    && modifiers.hasModifierProperty(PsiModifier.FINAL)
+                    && modifiers.hasModifierProperty(PsiModifier.PUBLIC)
+                    && ExpressionUtils.isZeroLengthArrayConstruction(field.getInitializer())) {
+                  registerError(expression, typeClass, field);
+                  return;
+                }
+              }
+            }
+          }
+        }
+        super.visitNewExpression(expression);
+      }
+    };
+  }
+}

plugins/InspectionGadgets/src/inspectionDescriptions/UnnecessaryEmptyArrayUsage.html

@@ -0,0 +1,8 @@
+<html>
+<body>
+Reports on allocations of arrays with known lengths of zero when there is a constant for that in the class of array's type.
+<!-- tooltip end -->
+<p>
+
+</body>
+</html>