diff --git a/java/java-impl/src/com/intellij/psi/impl/source/codeStyle/javadoc/CommentFormatter.java b/java/java-impl/src/com/intellij/psi/impl/source/codeStyle/javadoc/CommentFormatter.java
index 5949e58b6a1d..5aeaf48bb529 100644
--- a/java/java-impl/src/com/intellij/psi/impl/source/codeStyle/javadoc/CommentFormatter.java
+++ b/java/java-impl/src/com/intellij/psi/impl/source/codeStyle/javadoc/CommentFormatter.java
@@ -19,6 +19,9 @@ import com.intellij.util.IncorrectOperationException;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
+import java.util.Arrays;
+import java.util.stream.Collectors;
+
 /**
  * @author max
  */
@@ -83,12 +86,7 @@ public class CommentFormatter {
 
   private static String stripSpaces(String text) {
     String[] lines = LineTokenizer.tokenize(text.toCharArray(), false);
-    StringBuilder buf = new StringBuilder(text.length());
-    for (int i = 0; i < lines.length; i++) {
-      if (i > 0) buf.append('\n');
-      buf.append(rTrim(lines[i]));
-    }
-    return buf.toString();
+    return Arrays.stream(lines).map(CommentFormatter::rTrim).collect(Collectors.joining("\n"));
   }
 
   private static String rTrim(String text) {
diff --git a/java/java-impl/src/com/intellij/refactoring/rename/JavaNameSuggestionProvider.java b/java/java-impl/src/com/intellij/refactoring/rename/JavaNameSuggestionProvider.java
index baa831179977..d00fcf2aad11 100644
--- a/java/java-impl/src/com/intellij/refactoring/rename/JavaNameSuggestionProvider.java
+++ b/java/java-impl/src/com/intellij/refactoring/rename/JavaNameSuggestionProvider.java
@@ -30,6 +30,7 @@ import com.intellij.util.containers.ContainerUtil;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.*;
+import java.util.stream.Collectors;
 
 public class JavaNameSuggestionProvider implements NameSuggestionProvider {
   @Override
@@ -102,13 +103,8 @@ public class JavaNameSuggestionProvider implements NameSuggestionProvider {
       prefix = codeStyleManager.getPrefixByVariableKind(kind);
       if (kind == VariableKind.STATIC_FINAL_FIELD) {
         final String[] words = NameUtil.splitNameIntoWords(name);
-        StringBuilder buffer = new StringBuilder();
-        for (int i = 0; i < words.length; i++) {
-          String word = words[i];
-          if (i > 0) buffer.append('_');
-          buffer.append(StringUtil.toUpperCase(word));
-        }
-        return new String[] {buffer.toString()};
+        String buffer = Arrays.stream(words).map(StringUtil::toUpperCase).collect(Collectors.joining("_"));
+        return new String[] {buffer};
       }
     }
     final List<String> result = new ArrayList<>();
@@ -117,7 +113,7 @@ public class JavaNameSuggestionProvider implements NameSuggestionProvider {
       name = name.substring(prefix.length());
       result.add(suggestProperlyCasedName(prefix, NameUtil.splitNameIntoWords(name)));
     }
-    result.add(suggestProperlyCasedName(prefix, NameUtil.splitNameIntoWords(name.toLowerCase())));
+    result.add(suggestProperlyCasedName(prefix, NameUtil.splitNameIntoWords(name.toLowerCase(Locale.ENGLISH))));
     return ArrayUtil.toStringArray(result);
   }
 
diff --git a/platform/lang-impl/src/com/intellij/formatting/commandLine/FormatterStarter.java b/platform/lang-impl/src/com/intellij/formatting/commandLine/FormatterStarter.java
index 1d716225bd3d..4db7befad958 100644
--- a/platform/lang-impl/src/com/intellij/formatting/commandLine/FormatterStarter.java
+++ b/platform/lang-impl/src/com/intellij/formatting/commandLine/FormatterStarter.java
@@ -140,11 +140,6 @@ public class FormatterStarter implements ApplicationStarter {
   }
 
   private static void logArgs(@NotNull String[] args) {
-    StringBuilder sb = new StringBuilder();
-    for (String arg : args) {
-      if (sb.length() > 0) sb.append(",");
-      sb.append(arg);
-    }
-    LOG.info("Arguments: " + sb);
+    LOG.info("Arguments: " + String.join(",", args));
   }
 }
diff --git a/platform/platform-api/src/com/intellij/openapi/keymap/KeymapUtil.java b/platform/platform-api/src/com/intellij/openapi/keymap/KeymapUtil.java
index d4c027ba2614..64425df12c29 100644
--- a/platform/platform-api/src/com/intellij/openapi/keymap/KeymapUtil.java
+++ b/platform/platform-api/src/com/intellij/openapi/keymap/KeymapUtil.java
@@ -36,8 +36,9 @@ import org.jetbrains.annotations.Nullable;
 import javax.swing.*;
 import java.awt.*;
 import java.awt.event.*;
-import java.util.*;
 import java.util.List;
+import java.util.*;
+import java.util.stream.Collectors;
 
 public class KeymapUtil {
 
@@ -263,15 +264,7 @@ public class KeymapUtil {
     if (shortcuts.length == 0) {
       return "";
     }
-    StringBuilder buffer = new StringBuilder();
-    for (int i = 0; i < shortcuts.length; i++) {
-      Shortcut shortcut = shortcuts[i];
-      if (i > 0) {
-        buffer.append(' ');
-      }
-      buffer.append(getShortcutText(shortcut));
-    }
-    return buffer.toString();
+    return Arrays.stream(shortcuts).map(KeymapUtil::getShortcutText).collect(Collectors.joining(" "));
   }
 
   /**
diff --git a/platform/testFramework/src/com/intellij/testFramework/PlatformTestUtil.java b/platform/testFramework/src/com/intellij/testFramework/PlatformTestUtil.java
index 4ae85bce143e..8f4440c402ad 100644
--- a/platform/testFramework/src/com/intellij/testFramework/PlatformTestUtil.java
+++ b/platform/testFramework/src/com/intellij/testFramework/PlatformTestUtil.java
@@ -509,17 +509,8 @@ public class PlatformTestUtil {
     return print(Arrays.asList(objects));
   }
 
-  public static String print(Collection c) {
-    StringBuilder result = new StringBuilder();
-    for (Iterator iterator = c.iterator(); iterator.hasNext();) {
-      Object each = iterator.next();
-      result.append(toString(each, null));
-      if (iterator.hasNext()) {
-        result.append("\n");
-      }
-    }
-
-    return result.toString();
+  public static String print(Collection<?> c) {
+    return c.stream().map(each -> toString(each, null)).collect(Collectors.joining("\n"));
   }
 
   public static String print(ListModel model) {
diff --git a/plugins/java-i18n/src/com/intellij/codeInspection/i18n/I18nizeConcatenationQuickFix.java b/plugins/java-i18n/src/com/intellij/codeInspection/i18n/I18nizeConcatenationQuickFix.java
index 3d323928220a..31a6d17eabc3 100644
--- a/plugins/java-i18n/src/com/intellij/codeInspection/i18n/I18nizeConcatenationQuickFix.java
+++ b/plugins/java-i18n/src/com/intellij/codeInspection/i18n/I18nizeConcatenationQuickFix.java
@@ -30,9 +30,9 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
-import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.stream.Collectors;
 
 public class I18nizeConcatenationQuickFix extends I18nizeQuickFix{
   private static final Logger LOG = Logger.getInstance("#com.intellij.codeInsight.i18n.I18nizeConcatenationQuickFix");
@@ -71,15 +71,7 @@ public class I18nizeConcatenationQuickFix extends I18nizeQuickFix{
   }
 
   private static String composeParametersText(final List<PsiExpression> args) {
-    final StringBuilder result = new StringBuilder();
-    for (Iterator<PsiExpression> iterator = args.iterator(); iterator.hasNext();) {
-      PsiExpression psiExpression = iterator.next();
-      result.append(psiExpression.getText());
-      if (iterator.hasNext()) {
-        result.append(",");
-      }
-    }
-    return result.toString();
+    return args.stream().map(PsiExpression::getText).collect(Collectors.joining(","));
   }
 
   @Override