IPP: fix off-by-one error (IDEA-185274)

plugins/IntentionPowerPak/src/com/siyeh/ipp/concatenation/ReplaceFormatStringWithConcatenationIntention.java

@@ -112,7 +112,7 @@ public class ReplaceFormatStringWithConcatenationIntention extends Intention {
       start = end + 2;
       end = value.indexOf("%s", start);
     }
-    if (start < value.length() - 1) {
+    if (start < value.length()) {
       if (builder.length() > 0) {
         builder.append('+');
       }

plugins/IntentionPowerPak/testSrc/com/siyeh/ipp/concatenation/ReplaceFormatStringWithConcatenationIntentionTest.java

@@ -1,24 +1,10 @@
-/*
- * Copyright 2000-2017 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.
- */
+// Copyright 2000-2018 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.ipp.concatenation;
 
 import com.siyeh.ipp.IPPTestCase;
-import junit.framework.TestCase;
 
 /**
+ * @see ReplaceFormatStringWithConcatenationIntention
  * @author Bas Leijdekkers
  */
 public class ReplaceFormatStringWithConcatenationIntentionTest extends IPPTestCase {
@@ -94,4 +80,18 @@ public class ReplaceFormatStringWithConcatenationIntentionTest extends IPPTestCa
            "  }" +
            "}");
   }
+
+  public void testSingleCharacterSuffix() {
+    doTest("class Idempotent {" +
+           "  String x() {" +
+           "    return String./*_Replace 'String.format()' with concatenation*/format(\"%s.\", \"foo\");" +
+           "  }" +
+           "}",
+
+           "class Idempotent {" +
+           "  String x() {" +
+           "    return \"foo\" + \".\";" +
+           "  }" +
+           "}");
+  }
 }