RedundantStringOperationInspection: fixes after review IDEA-CR-25339

1. messages cleanup
2. new StringBuilder(""). PrintStream.println("") are warned

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/afterPrintlnEmpty.java

@@ -0,0 +1,6 @@
+// "Delete element" "true"
+class Foo {
+  public static void main(String[] args) {
+    System.out.println();
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/afterStringBuilderAppendEmpty.java

@@ -1,4 +1,4 @@
-// "Remove redundant 'append' call" "true"
+// "Remove redundant 'append()' call" "true"
 class Foo {
   public static void main(String[] args) {
     StringBuilder sb = new StringBuilder();

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/afterStringBuilderEmpty.java

@@ -0,0 +1,6 @@
+// "Delete element" "true"
+class Foo {
+  public static void main(String[] args) {
+    StringBuilder s = new StringBuilder();
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/afterStringIntern.java

@@ -1,4 +1,4 @@
-// "Remove redundant 'intern' call" "true"
+// "Remove redundant 'intern()' call" "true"
 class Foo {
   private static final String x = ("Hello "+"World"+'!');
 }

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/afterStringToString.java

@@ -1,4 +1,4 @@
-// "Remove redundant 'toString' call" "true"
+// "Remove redundant 'toString()' call" "true"
 class Foo {
   public static void main(String[] args) {
       /*valuable comment!!!*/

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/beforeObjectToString.java

@@ -1,4 +1,4 @@
-// "Remove redundant 'toString' call" "false"
+// "Remove redundant 'toString()' call" "false"
 class Foo {
   public static void main(String[] args) {
     Object[] a = args;

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/beforePrintlnEmpty.java

@@ -0,0 +1,6 @@
+// "Delete element" "true"
+class Foo {
+  public static void main(String[] args) {
+    System.out.println("<caret>");
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/beforeStringBuilderAppendEmpty.java

@@ -1,4 +1,4 @@
-// "Remove redundant 'append' call" "true"
+// "Remove redundant 'append()' call" "true"
 class Foo {
   public static void main(String[] args) {
     StringBuilder sb = new StringBuilder();

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/beforeStringBuilderEmpty.java

@@ -0,0 +1,6 @@
+// "Delete element" "true"
+class Foo {
+  public static void main(String[] args) {
+    StringBuilder s = new StringBuilder(("<caret>"));
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/beforeStringIntern.java

@@ -1,4 +1,4 @@
-// "Remove redundant 'intern' call" "true"
+// "Remove redundant 'intern()' call" "true"
 class Foo {
   private static final String x = ("Hello "+"World"+'!').inte<caret>rn();
 }

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/beforeStringInternNonConst.java

@@ -1,4 +1,4 @@
-// "Remove redundant 'intern' call" "false"
+// "Remove redundant 'intern()' call" "false"
 class Foo {
   private static final String x = ("Hello "+"World".trim()+'!').inte<caret>rn();
 }

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/beforeStringToString.java

@@ -1,4 +1,4 @@
-// "Remove redundant 'toString' call" "true"
+// "Remove redundant 'toString()' call" "true"
 class Foo {
   public static void main(String[] args) {
     String s = args[0].toString<caret>(/*valuable comment!!!*/);

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

@@ -2229,7 +2229,8 @@ return.of.field.with.mutable.type.problem.descriptor=Return of {0} field <code>{
 ignore.private.methods.option=Ignore assignments in and returns from private methods
 
 inspection.redundant.string.operation.display.name=Redundant String operation
-inspection.redundant.string.remove.fix.name=Remove redundant ''{0}'' call
+inspection.redundant.string.remove.fix.name=Remove redundant ''{0}()'' call
 inspection.redundant.string.replace.with.qualifier.fix.family.name=Replace with qualifier
-inspection.redundant.string.message=<code>#ref</code> is redundant #loc
-inspection.redundant.string.intern.on.constant.message=<code>.#ref()</code> on compile-time constant is unnecessary #loc
+inspection.redundant.string.call.message=Call to <code>#ref</code> is redundant #loc
+inspection.redundant.string.argument.message=Unnecessary empty string argument
+inspection.redundant.string.intern.on.constant.message=Call to <code>#ref</code> on compile-time constant is unnecessary #loc

plugins/InspectionGadgets/src/com/siyeh/ig/redundancy/RedundantStringOperationInspection.java

@@ -1,6 +1,7 @@
 // Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package com.siyeh.ig.redundancy;
 
+import com.intellij.codeInsight.daemon.impl.quickfix.DeleteElementFix;
 import com.intellij.codeInspection.*;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.TextRange;
@@ -32,6 +33,8 @@ public class RedundantStringOperationInspection extends AbstractBaseJavaLocalIns
   private static final CallMatcher STRING_BUILDER_APPEND =
     CallMatcher.instanceCall(CommonClassNames.JAVA_LANG_ABSTRACT_STRING_BUILDER, "append")
       .parameterTypes(JAVA_LANG_STRING);
+  private static final CallMatcher PRINTSTREAM_PRINTLN = CallMatcher.instanceCall("java.io.PrintStream", "println")
+    .parameterTypes(JAVA_LANG_STRING);
 
   @NotNull
   @Override
@@ -42,23 +45,51 @@ public class RedundantStringOperationInspection extends AbstractBaseJavaLocalIns
         PsiExpression qualifier = call.getMethodExpression().getQualifierExpression();
         if (qualifier != null) {
           if (STRING_TO_STRING.test(call)) {
-            registerProblem(call, "inspection.redundant.string.message");
+            registerProblem(call, "inspection.redundant.string.call.message");
           }
           else if (STRING_SUBSTRING.test(call)) {
             processSubstring(call);
           }
           else if (STRING_BUILDER_APPEND.test(call)) {
-            PsiExpression arg = call.getArgumentList().getExpressions()[0];
-            if (ExpressionUtils.isLiteral(PsiUtil.skipParenthesizedExprDown(arg), "")) {
-              registerProblem(call, "inspection.redundant.string.message");
+            if (getSingleEmptyStringArgument(call) != null) {
+              registerProblem(call, "inspection.redundant.string.call.message");
             }
           }
           else if (STRING_INTERN.test(call) && PsiUtil.isConstantExpression(qualifier)) {
             registerProblem(call, "inspection.redundant.string.intern.on.constant.message");
           }
+          else if (PRINTSTREAM_PRINTLN.test(call)) {
+            checkUnnecessaryEmptyStringArgument(call);
+          }
         }
       }
 
+      @Override
+      public void visitNewExpression(PsiNewExpression expression) {
+        PsiJavaCodeReferenceElement classRef = expression.getClassReference();
+        if (classRef == null) return;
+        String className = classRef.getQualifiedName();
+        if (CommonClassNames.JAVA_LANG_STRING_BUILDER.equals(className) || CommonClassNames.JAVA_LANG_STRING_BUFFER.equals(className)) {
+          checkUnnecessaryEmptyStringArgument(expression);
+        }
+      }
+
+      private void checkUnnecessaryEmptyStringArgument(PsiCall call) {
+        PsiExpression argument = getSingleEmptyStringArgument(call);
+        if (argument != null) {
+          holder.registerProblem(argument, InspectionGadgetsBundle.message("inspection.redundant.string.argument.message"),
+                                 ProblemHighlightType.LIKE_UNUSED_SYMBOL, new DeleteElementFix(argument));
+        }
+      }
+
+      private PsiExpression getSingleEmptyStringArgument(PsiCall call) {
+        PsiExpressionList argList = call.getArgumentList();
+        if (argList == null) return null;
+        PsiExpression[] args = argList.getExpressions();
+        if (args.length != 1) return null;
+        return ExpressionUtils.isLiteral(PsiUtil.skipParenthesizedExprDown(args[0]), "") ? args[0] : null;
+      }
+
       private void processSubstring(PsiMethodCallExpression call) {
         PsiExpression[] args = call.getArgumentList().getExpressions();
         if (!ExpressionUtils.isZero(args[0])) return;
@@ -72,7 +103,7 @@ public class RedundantStringOperationInspection extends AbstractBaseJavaLocalIns
             return;
           }
         }
-        registerProblem(call, "inspection.redundant.string.message");
+        registerProblem(call, "inspection.redundant.string.call.message");
       }
 
       private void registerProblem(PsiMethodCallExpression call, @NotNull @PropertyKey(resourceBundle = BUNDLE) String key) {