Address some perf issues reported by PMD 2.2:

Redundant Field Initializer 52
Avoid Instantiating Objects In Loops 15
Consecutive Appends Should Reuse 14
Inefficient String Buffering 8
Use String Buffer For String Appends 7
Optimizable To Array Call 6
Append Character With Char 5
Insufficient String Buffer Declaration 3
Inefficient Empty String Check 3
Add Empty String 2
Avoid File Stream 1
Use Index Of Char 1
Simplify Starts With 1

src/de.hpi.swa.trufflesqueak.launcher/src/de/hpi/swa/trufflesqueak/launcher/TruffleSqueakLauncher.java

@@ -30,14 +30,14 @@
 import de.hpi.swa.trufflesqueak.shared.SqueakLanguageOptions;
 
 public final class TruffleSqueakLauncher extends AbstractLanguageLauncher {
-    private boolean headless = false;
-    private boolean printImagePath = false;
-    private boolean quiet = false;
+    private boolean headless;
+    private boolean printImagePath;
+    private boolean quiet;
     private String[] imageArguments = new String[0];
-    private String imagePath = null;
-    private String sourceCode = null;
-    private boolean enableTranscriptForwarding = false;
-    private String logHandlerMode = null;
+    private String imagePath;
+    private String sourceCode;
+    private boolean enableTranscriptForwarding;
+    private String logHandlerMode;
 
     public static void main(final String[] arguments) throws RuntimeException {
         new TruffleSqueakLauncher().launch(arguments);
@@ -51,7 +51,7 @@ protected List<String> preprocessArguments(final List<String> arguments, final M
             if (isExistingImageFile(arg)) {
                 imagePath = Paths.get(arg).toAbsolutePath().toString();
                 final List<String> remainingArguments = arguments.subList(i + 1, arguments.size());
-                imageArguments = remainingArguments.toArray(new String[remainingArguments.size()]);
+                imageArguments = remainingArguments.toArray(new String[0]);
                 break;
             } else if (SqueakLanguageOptions.CODE_FLAG.equals(arg) || SqueakLanguageOptions.CODE_FLAG_SHORT.equals(arg)) {
                 sourceCode = arguments.get(++i);
@@ -128,7 +128,7 @@ protected int execute(final Context.Builder contextBuilder) {
         } catch (final IllegalArgumentException e) {
             if (e.getMessage().contains("Could not find option with name " + SqueakLanguageConfig.ID)) {
                 final String thisPackageName = getClass().getPackage().getName();
-                final String parentPackageName = thisPackageName.substring(0, thisPackageName.lastIndexOf("."));
+                final String parentPackageName = thisPackageName.substring(0, thisPackageName.lastIndexOf('.'));
                 throw abort(String.format("Failed to load TruffleSqueak. Please ensure '%s' is on the Java class path.", parentPackageName));
             } else {
                 throw e;

src/de.hpi.swa.trufflesqueak.shared/src/de/hpi/swa/trufflesqueak/shared/LogHandlerAccessor.java

@@ -40,7 +40,6 @@ public final class LogHandlerAccessor {
     private static boolean firstTime = true;
 
     public static Handler createLogHandler(final String mode) {
-        PrintStream output = null;
         switch (mode) {
             case "mapped":
                 if (firstTime) {
@@ -59,16 +58,14 @@ public static Handler createLogHandler(final String mode) {
                     firstTime = false;
                     println("TruffleSqueak log handler logging to standard err");
                 }
-                output = System.err;
-                break;
+                return new StandardPrintStreamHandler(System.err);
             default:
                 if (firstTime) {
                     firstTime = false;
                     println("TruffleSqueak log handler logging to standard out");
                 }
-                output = System.out;
+                return new StandardPrintStreamHandler(System.out);
         }
-        return new StandardPrintStreamHandler(output);
     }
 
     protected static Path getLogPath() {

src/de.hpi.swa.trufflesqueak.test/src/de/hpi/swa/trufflesqueak/test/AbstractSqueakTestCaseWithImage.java

@@ -9,6 +9,8 @@
 
 import java.io.File;
 import java.io.FileFilter;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
@@ -126,13 +128,13 @@ private static String getPathToTestImage() {
     }
 
     private static String getPathToTestImage(final String imageName) {
-        File currentDirectory = new File(System.getProperty("user.dir"));
+        Path currentDirectory = Paths.get(System.getProperty("user.dir")).toAbsolutePath();
         while (currentDirectory != null) {
-            final String pathToImage = currentDirectory.getAbsolutePath() + File.separator + "images" + File.separator + imageName;
-            if (new File(pathToImage).exists()) {
-                return pathToImage;
+            final File file = currentDirectory.resolve("images").resolve(imageName).toFile();
+            if (file.exists()) {
+                return file.getAbsolutePath();
             }
-            currentDirectory = currentDirectory.getParentFile();
+            currentDirectory = currentDirectory.getParent();
         }
         return null;
     }
@@ -274,17 +276,17 @@ private static String[] truffleSqueakTestCaseNames() {
                 testCaseNames.add(classDirectories.getName().substring(0, classDirectories.getName().lastIndexOf(".class")));
             }
         }
-        return testCaseNames.toArray(new String[testCaseNames.size()]);
+        return testCaseNames.toArray(new String[0]);
     }
 
     protected static final String getPathToInImageCode() {
-        File currentDirectory = new File(System.getProperty("user.dir"));
+        Path currentDirectory = Paths.get(System.getProperty("user.dir")).toAbsolutePath();
         while (currentDirectory != null) {
-            final String pathToImage = currentDirectory.getAbsolutePath() + File.separator + "src" + File.separator + "image" + File.separator + "src";
-            if (new File(pathToImage).isDirectory()) {
-                return pathToImage;
+            final File file = currentDirectory.resolve("src").resolve("image").resolve("src").toFile();
+            if (file.isDirectory()) {
+                return file.getAbsolutePath();
             }
-            currentDirectory = currentDirectory.getParentFile();
+            currentDirectory = currentDirectory.getParent();
         }
         return null;
     }

src/de.hpi.swa.trufflesqueak.test/src/de/hpi/swa/trufflesqueak/test/SqueakSUnitTest.java

@@ -27,6 +27,7 @@
 
 import de.hpi.swa.trufflesqueak.test.SqueakTests.SqueakTest;
 import de.hpi.swa.trufflesqueak.test.SqueakTests.TestType;
+import de.hpi.swa.trufflesqueak.util.MiscUtils;
 
 /**
  * Run tests from the Squeak image.
@@ -66,7 +67,7 @@ public class SqueakSUnitTest extends AbstractSqueakTestCaseWithImage {
 
     @Parameter public SqueakTest test;
 
-    private static boolean truffleSqueakPackagesLoaded = false;
+    private static boolean truffleSqueakPackagesLoaded;
     private static boolean stopRunningSuite;
 
     @Parameters(name = "{0} (#{index})")
@@ -76,7 +77,7 @@ public static Collection<SqueakTest> getParameters() {
 
     private static Stream<SqueakTest> selectTestsToRun() {
         final String toRun = System.getProperty(TEST_CLASS_PROPERTY);
-        if (toRun != null && !toRun.trim().isEmpty()) {
+        if (toRun != null && !MiscUtils.isBlank(toRun)) {
             return SqueakTests.getTestsToRun(toRun);
         }
         return SqueakTests.allTests();

src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/aot/SqueakDisplaySubstitutions.java

@@ -67,17 +67,17 @@ final class Target_de_hpi_swa_trufflesqueak_io_SqueakDisplay implements SqueakDi
     private Cursor cursor = WordFactory.nullPointer();
     private NativeObject bitmap;
     @CompilationFinal private int inputSemaphoreIndex;
-    private boolean deferUpdates = false;
-    private boolean textureDirty = false;
+    private boolean deferUpdates;
+    private boolean textureDirty;
     private int width;
     private int height;
     private int bpp = 4; // TODO: for 32bit only!
 
     private int lastMouseXPos;
     private int lastMouseYPos;
-    private int button = 0;
-    private int key = 0;
-    private boolean isKeyDown = false;
+    private int button;
+    private int key;
+    private boolean isKeyDown;
 
     Target_de_hpi_swa_trufflesqueak_io_SqueakDisplay(final SqueakImageContext image) {
         this.image = image;

src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/image/SqueakImageContext.java

@@ -95,9 +95,9 @@ public final class SqueakImageContext {
     public final NativeObject runWithInSelector = new NativeObject(this);
     public final ArrayObject primitiveErrorTable = new ArrayObject(this);
     public final ArrayObject specialSelectors = new ArrayObject(this);
-    @CompilationFinal private ClassObject smallFloatClass = null;
-    @CompilationFinal private ClassObject byteSymbolClass = null;
-    @CompilationFinal private ClassObject foreignObjectClass = null;
+    @CompilationFinal private ClassObject smallFloatClass;
+    @CompilationFinal private ClassObject byteSymbolClass;
+    @CompilationFinal private ClassObject foreignObjectClass;
 
     public final ArrayObject specialObjectsArray = new ArrayObject(this);
     public final ClassObject metaClass = new ClassObject(this);
@@ -134,14 +134,14 @@ public final class SqueakImageContext {
     @CompilationFinal private SqueakImage squeakImage;
 
     /* Stack Management */
-    public int stackDepth = 0;
+    public int stackDepth;
     public ContextObject lastSeenContext;
 
-    @CompilationFinal private ClassObject compilerClass = null;
-    @CompilationFinal private ClassObject parserClass = null;
-    private PointersObject parserSharedInstance = null;
-    @CompilationFinal private PointersObject scheduler = null;
-    @CompilationFinal private ClassObject wideStringClass = null;
+    @CompilationFinal private ClassObject compilerClass;
+    @CompilationFinal private ClassObject parserClass;
+    private PointersObject parserSharedInstance;
+    @CompilationFinal private PointersObject scheduler;
+    @CompilationFinal private ClassObject wideStringClass;
 
     /* Plugins */
     public final B2D b2d = new B2D(this);
@@ -152,9 +152,9 @@ public final class SqueakImageContext {
 
     /* Error detection for headless execution */
     @CompilationFinal(dimensions = 1) public static final byte[] DEBUG_ERROR_SELECTOR_NAME = "debugError:".getBytes();
-    @CompilationFinal private NativeObject debugErrorSelector = null;
+    @CompilationFinal private NativeObject debugErrorSelector;
     @CompilationFinal(dimensions = 1) public static final byte[] DEBUG_SYNTAX_ERROR_SELECTOR_NAME = "debugSyntaxError:".getBytes();
-    @CompilationFinal private NativeObject debugSyntaxErrorSelector = null;
+    @CompilationFinal private NativeObject debugSyntaxErrorSelector;
 
     public SqueakImageContext(final SqueakLanguage squeakLanguage, final SqueakLanguage.Env environment) {
         language = squeakLanguage;
@@ -517,9 +517,9 @@ public void setImagePath(final String path) {
     public String getImageDirectory() {
         final Path parent = Paths.get(getImagePath()).getParent();
         if (parent != null) {
-            return "" + parent.getFileName(); // Avoids NullPointerExceptions.
+            return parent.toString();
         } else {
-            throw SqueakException.create("`parent` should not be `null`.");
+            throw SqueakException.create("Could not determine image directory.");
         }
     }
 

src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/image/SqueakImageFlags.java

@@ -12,7 +12,7 @@
 
 public final class SqueakImageFlags {
     @CompilationFinal private long oldBaseAddress = -1;
-    @CompilationFinal private int fullScreenFlag = 0;
+    @CompilationFinal private int fullScreenFlag;
     @CompilationFinal private int imageFloatsBigEndian;
     @CompilationFinal private boolean flagInterpretedMethods;
     @CompilationFinal private boolean preemptionYields;

src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/image/SqueakImageReader.java

@@ -48,11 +48,11 @@ public final class SqueakImageReader {
     private int headerFlags;
     private short maxExternalSemaphoreTableSize;
     private long firstSegmentSize;
-    private int position = 0;
+    private int position;
     private long currentAddressSwizzle;
     private final byte[] emptyBytes = new byte[0];
 
-    private SqueakImageChunk freePageList = null;
+    private SqueakImageChunk freePageList;
 
     private SqueakImageReader(final SqueakImageContext image) {
         final TruffleFile truffleFile = image.env.getPublicTruffleFile(image.getImagePath());

src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/interop/JavaObjectWrapper.java

@@ -165,7 +165,7 @@ public Object getMembers(@SuppressWarnings("unused") final boolean includeIntern
             members.add(WRAPPED_MEMBER);
             members.addAll(getFields().keySet());
             members.addAll(getMethods().keySet());
-            cachedMembers = new InteropArray(members.toArray(new String[members.size()]));
+            cachedMembers = new InteropArray(members.toArray(new String[0]));
         }
         return cachedMembers;
     }

src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/io/SqueakDisplay.java

@@ -28,7 +28,6 @@
 import java.io.File;
 import java.io.IOException;
 import java.util.ArrayDeque;
-import java.util.Iterator;
 import java.util.List;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
@@ -74,11 +73,10 @@ public final class SqueakDisplay implements SqueakDisplayInterface {
 
     @CompilationFinal private int inputSemaphoreIndex = -1;
 
-    public int buttons = 0;
-    private Dimension rememberedWindowSize = null;
-    private Point rememberedWindowLocation = null;
-    private boolean deferUpdates = false;
-    private int[] cursorMergedWords = new int[SqueakIOConstants.CURSOR_HEIGHT];
+    public int buttons;
+    private Dimension rememberedWindowSize;
+    private Point rememberedWindowLocation;
+    private boolean deferUpdates;
 
     public SqueakDisplay(final SqueakImageContext image) {
         this.image = image;
@@ -313,16 +311,13 @@ public void setCursor(final int[] cursorWords, final int[] mask, final int width
         canvas.setCursor(cursor);
     }
 
-    private int[] mergeCursorWithMask(final int[] cursorWords, final int[] maskWords) {
-        int cursorWord;
-        int maskWord;
-        int bit;
-        int merged;
+    private static int[] mergeCursorWithMask(final int[] cursorWords, final int[] maskWords) {
+        final int[] cursorMergedWords = new int[SqueakIOConstants.CURSOR_HEIGHT];
         for (int y = 0; y < SqueakIOConstants.CURSOR_HEIGHT; y++) {
-            cursorWord = cursorWords[y];
-            maskWord = maskWords[y];
-            bit = 0x80000000;
-            merged = 0;
+            final int cursorWord = cursorWords[y];
+            final int maskWord = maskWords[y];
+            int bit = 0x80000000;
+            int merged = 0;
             for (int x = 0; x < SqueakIOConstants.CURSOR_WIDTH; x++) {
                 merged = merged | (maskWord & bit) >> x | (cursorWord & bit) >> x + 1;
                 bit = bit >>> 1;
@@ -433,14 +428,8 @@ public void drop(final DropTargetDropEvent dtde) {
                     dtde.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
                     try {
                         @SuppressWarnings("unchecked")
-                        final List<File> l = (List<File>) transferable.getTransferData(DataFlavor.javaFileListFlavor);
-                        final Iterator<File> iter = l.iterator();
-                        final String[] fileList = new String[l.size()];
-                        int i = 0;
-                        while (iter.hasNext()) {
-                            fileList[i++] = iter.next().getCanonicalPath();
-                        }
-                        image.dropPluginFileList = fileList;
+                        final List<File> fileList = (List<File>) transferable.getTransferData(DataFlavor.javaFileListFlavor);
+                        image.dropPluginFileList = fileList.toArray(new String[0]);
                         addDragEvent(DRAG.DROP, dtde.getLocation());
                         dtde.getDropTargetContext().dropComplete(true);
                         return;

src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/model/ClassObject.java

@@ -53,7 +53,7 @@ public final class ClassObject extends AbstractSqueakObjectWithClassAndHash {
     private final CyclicAssumption methodDictStable = new CyclicAssumption("Method dictionary stability");
     private final CyclicAssumption classFormatStable = new CyclicAssumption("Class format stability");
 
-    @CompilationFinal private boolean instancesAreClasses = false;
+    @CompilationFinal private boolean instancesAreClasses;
 
     private ClassObject superclass;
     @CompilationFinal private VariablePointersObject methodDict;
@@ -445,7 +445,7 @@ public Object[] listInteropMembers() {
             }
             lookupClass = lookupClass.getSuperclassOrNull();
         }
-        return methodNames.toArray(new String[methodNames.size()]);
+        return methodNames.toArray(new String[0]);
     }
 
     public int getBasicInstanceSize() {

src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/model/CompiledCodeObject.java

@@ -63,7 +63,7 @@ public enum SLOT_IDENTIFIER {
     @CompilationFinal protected int numArgs;
     @CompilationFinal protected int numLiterals;
     @CompilationFinal protected boolean hasPrimitive;
-    @CompilationFinal protected boolean needsLargeFrame = false;
+    @CompilationFinal protected boolean needsLargeFrame;
     @CompilationFinal protected int numTemps;
 
     @CompilationFinal(dimensions = 1) private CompiledBlockObject[] innerBlocks;

src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/model/CompiledMethodObject.java

@@ -74,19 +74,10 @@ public String toString() {
         return className + ">>" + getNotNilSelector();
     }
 
-    public String getNotNilSelector() {
+    private String getNotNilSelector() {
         CompilerAsserts.neverPartOfCompilation();
-        String selector = "DoIt";
         final NativeObject selectorObj = getCompiledInSelector();
-        if (selectorObj != null) {
-            selector = selectorObj.asStringUnsafe();
-        } else if (getNumArgs() > 0) {
-            selector += ":";
-            for (int i = 1; i < getNumArgs(); i++) {
-                selector += "with:";
-            }
-        }
-        return selector;
+        return selectorObj == null ? "DoIt" : selectorObj.asStringUnsafe();
     }
 
     @Override

src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/model/ContextObject.java

@@ -44,8 +44,8 @@ public final class ContextObject extends AbstractSqueakObjectWithHash {
     @CompilationFinal private MaterializedFrame truffleFrame;
     @CompilationFinal private PointersObject process;
     @CompilationFinal private int size;
-    private boolean hasModifiedSender = false;
-    private boolean escaped = false;
+    private boolean hasModifiedSender;
+    private boolean escaped;
 
     private ContextObject(final SqueakImageContext image, final long hash) {
         super(image, hash);

src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/model/FloatObject.java

@@ -146,7 +146,7 @@ public void write(final SqueakImageWriter writer) {
     @Override
     public String toString() {
         CompilerAsserts.neverPartOfCompilation();
-        return "" + doubleValue;
+        return Double.toString(doubleValue);
     }
 
     public FloatObject shallowCopy() {