replacing == and != for strings where appropriate

java/java-impl/src/com/intellij/codeInsight/daemon/impl/quickfix/AddDefaultConstructorFix.java

@@ -33,7 +33,7 @@ public class AddDefaultConstructorFix extends AddMethodFix {
   }
 
   private static String generateConstructor(final String className, @PsiModifier.ModifierConstant final String modifier) {
-    if (modifier == PsiModifier.PACKAGE_LOCAL) {
+    if (modifier.equals(PsiModifier.PACKAGE_LOCAL)) {
       return className + "() {}";
     }
     return modifier + " " + className + "() {}";

java/java-psi-api/src/com/intellij/codeInsight/NullableNotNullManager.java

@@ -137,7 +137,7 @@ public class NullableNotNullManager implements PersistentStateComponent<Element>
     if (DEFAULT_NULLABLES.length != getNullables().size() || DEFAULT_NOT_NULLS.length != getNotNulls().size()) {
       return false;
     }
-    if (myDefaultNotNull != AnnotationUtil.NOT_NULL || myDefaultNullable != AnnotationUtil.NULLABLE) {
+    if (!myDefaultNotNull.equals(AnnotationUtil.NOT_NULL) || !myDefaultNullable.equals(AnnotationUtil.NULLABLE)) {
       return false;
     }
     for (int i = 0; i < DEFAULT_NULLABLES.length; i++) {

platform/lang-impl/src/com/intellij/diagnostic/logging/DefaultLogFilterModel.java

@@ -153,7 +153,7 @@ public class DefaultLogFilterModel extends LogFilterModel {
     final String type = LogConsolePreferences.getType(line);
     Key contentType = type != null
                       ? LogConsolePreferences.getProcessOutputTypes(type)
-                      : (myPrevType == LogConsolePreferences.ERROR ? ProcessOutputTypes.STDERR : ProcessOutputTypes.STDOUT);
+                      : (myPrevType.equals(LogConsolePreferences.ERROR) ? ProcessOutputTypes.STDERR : ProcessOutputTypes.STDOUT);
     if (type != null) {
       myPrevType = type;
     }

platform/lang-impl/src/com/intellij/ide/impl/StructureViewWrapperImpl.java

@@ -377,7 +377,7 @@ public class StructureViewWrapperImpl implements StructureViewWrapper, Disposabl
     }
 
     public Object getData(@NonNls String dataId) {
-      if (dataId == myKey) return StructureViewWrapperImpl.this;
+      if (dataId.equals(myKey)) return StructureViewWrapperImpl.this;
       return null;
     }
   }

platform/lang-impl/src/com/intellij/refactoring/rename/inplace/RenameChooser.java

@@ -67,7 +67,7 @@ abstract class RenameChooser {
         dropHighlighters();
         final MarkupModel markupModel = myEditor.getMarkupModel();
 
-        if (selectedValue == ALL_OCCURRENCES) {
+        if (selectedValue.equals(ALL_OCCURRENCES)) {
           for (Pair<PsiElement, TextRange> pair : stringUsages) {
             final TextRange textRange = pair.second.shiftRight(pair.first.getTextOffset());
             final RangeHighlighter rangeHighlighter = markupModel.addRangeHighlighter(
@@ -96,7 +96,7 @@ abstract class RenameChooser {
       .setRequestFocus(true)
       .setItemChoosenCallback(new Runnable() {
         public void run() {
-          runRenameTemplate(list.getSelectedValue() == ALL_OCCURRENCES ? stringUsages : new ArrayList<Pair<PsiElement, TextRange>>());
+          runRenameTemplate(list.getSelectedValue().equals(ALL_OCCURRENCES) ? stringUsages : new ArrayList<Pair<PsiElement, TextRange>>());
         }
       })
       .addListener(new JBPopupAdapter() {

platform/platform-api/src/com/intellij/openapi/ui/LabeledComponent.java

@@ -107,7 +107,7 @@ public class LabeledComponent<Comp extends JComponent> extends JPanel implements
 
   public void setLabelLocation(@NonNls String borderConstrains) {
     String constrains = findBorderConstrains(borderConstrains);
-    if (constrains == null || constrains == myLabelConstraints) return;
+    if (constrains == null || constrains.equals(myLabelConstraints)) return;
     myLabelConstraints = borderConstrains;
     insertLabel();
   }

platform/smRunner/src/com/intellij/execution/testframework/sm/runner/TestSuiteStack.java

@@ -17,6 +17,8 @@ package com.intellij.execution.testframework.sm.runner;
 
 import com.intellij.execution.testframework.sm.SMTestRunnerConnectionUtil;
 import com.intellij.openapi.diagnostic.Logger;
+import com.intellij.openapi.util.text.StringUtil;
+import com.intellij.util.Function;
 import org.jetbrains.annotations.NonNls;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -124,17 +126,12 @@ public class TestSuiteStack {
       return EMPTY;
     }
 
-    final StringBuilder builder = new StringBuilder();
-    final String lastName = names[names.length - 1];
-    for (String name : names) {
-      builder.append('[').append(name).append(']');
-      //Here we can use != instead of !equals()
-      //noinspection StringEquality
-      if (name != lastName) {
-        builder.append("->");
+    return StringUtil.join(names, new Function<String, String>() {
+      @Override
+      public String fun(String s) {
+        return "[" + s + "]";
       }
-    }
-    return builder.toString();
+    }, "->");
   }
 
   public void clear() {

platform/util/src/com/intellij/openapi/diff/impl/highlighting/FragmentSide.java

@@ -93,7 +93,7 @@ public enum FragmentSide {
 
   public static FragmentSide chooseSide(DiffFragment oneSide) {
     LOG.assertTrue(oneSide.isOneSide());
-    LOG.assertTrue(oneSide.getText1() != oneSide.getText2());
+    LOG.assertTrue(!oneSide.getText1().equals(oneSide.getText2()));
     return oneSide.getText1() == null ? SIDE2 : SIDE1;
   }
 

plugins/groovy/src/org/jetbrains/plugins/groovy/mvc/MvcActionBase.java

@@ -3,6 +3,7 @@ package org.jetbrains.plugins.groovy.mvc;
 import com.intellij.openapi.actionSystem.ActionPlaces;
 import com.intellij.openapi.actionSystem.AnActionEvent;
 import com.intellij.openapi.actionSystem.DataKeys;
+import com.intellij.openapi.actionSystem.LangDataKeys;
 import com.intellij.openapi.module.Module;
 import com.intellij.openapi.module.ModuleManager;
 import com.intellij.openapi.project.DumbAwareAction;
@@ -29,7 +30,7 @@ public abstract class MvcActionBase extends DumbAwareAction {
 
   @Nullable
   public static Pair<MvcFramework, Module> guessFramework(AnActionEvent event) {
-    final Module module = event.getData(event.getPlace() == ActionPlaces.MAIN_MENU ? DataKeys.MODULE : DataKeys.MODULE_CONTEXT);
+    final Module module = event.getData(event.getPlace().equals(ActionPlaces.MAIN_MENU) ? LangDataKeys.MODULE : LangDataKeys.MODULE_CONTEXT);
 
     if (module != null) {
       MvcFramework commonPluginModuleFramework = MvcFramework.findCommonPluginModuleFramework(module);