8289908: Skip bounds check for cases when String is constructed from entirely used byte[]

Reviewed-by: prr, rriggs, aturbanov

src/java.base/share/classes/java/lang/String.java

@@ -484,7 +484,7 @@ public final class String
      */
     public String(byte[] bytes, int offset, int length, String charsetName)
             throws UnsupportedEncodingException {
-        this(bytes, offset, length, lookupCharset(charsetName));
+        this(lookupCharset(charsetName), bytes, checkBoundsOffCount(offset, length, bytes.length), length);
     }
 
     /**
@@ -517,10 +517,18 @@ public final class String
      *
      * @since  1.6
      */
-    @SuppressWarnings("removal")
     public String(byte[] bytes, int offset, int length, Charset charset) {
-        Objects.requireNonNull(charset);
+        this(Objects.requireNonNull(charset), bytes, checkBoundsOffCount(offset, length, bytes.length), length);
-        checkBoundsOffCount(offset, length, bytes.length);
+    }
+
+    /**
+     * This method does not do any precondition checks on its arguments.
+     * <p>
+     * Important: parameter order of this method is deliberately changed in order to
+     * disambiguate it against other similar methods of this class.
+     */
+    @SuppressWarnings("removal")
+    private String(Charset charset, byte[] bytes, int offset, int length) {
         if (length == 0) {
             this.value = "".value;
             this.coder = "".coder;
@@ -1370,7 +1378,7 @@ public final class String
      */
     public String(byte[] bytes, String charsetName)
             throws UnsupportedEncodingException {
-        this(bytes, 0, bytes.length, charsetName);
+        this(lookupCharset(charsetName), bytes, 0, bytes.length);
     }
 
     /**
@@ -1394,7 +1402,7 @@ public final class String
      * @since  1.6
      */
     public String(byte[] bytes, Charset charset) {
-        this(bytes, 0, bytes.length, charset);
+        this(Objects.requireNonNull(charset), bytes, 0, bytes.length);
     }
 
     /**
@@ -1424,7 +1432,7 @@ public final class String
      * @since  1.1
      */
     public String(byte[] bytes, int offset, int length) {
-        this(bytes, offset, length, Charset.defaultCharset());
+        this(Charset.defaultCharset(), bytes, checkBoundsOffCount(offset, length, bytes.length), length);
     }
 
     /**
@@ -1444,7 +1452,7 @@ public final class String
      * @since  1.1
      */
     public String(byte[] bytes) {
-        this(bytes, 0, bytes.length);
+        this(Charset.defaultCharset(), bytes, 0, bytes.length);
     }
 
     /**
@@ -4582,12 +4590,13 @@ public final class String
      * Check {@code offset}, {@code count} against {@code 0} and {@code length}
      * bounds.
      *
+     * @return  {@code offset} if the sub-range within bounds of the range
      * @throws  StringIndexOutOfBoundsException
      *          If {@code offset} is negative, {@code count} is negative,
      *          or {@code offset} is greater than {@code length - count}
      */
-    static void checkBoundsOffCount(int offset, int count, int length) {
+    static int checkBoundsOffCount(int offset, int count, int length) {
-        Preconditions.checkFromIndexSize(offset, count, length, Preconditions.SIOOBE_FORMATTER);
+        return Preconditions.checkFromIndexSize(offset, count, length, Preconditions.SIOOBE_FORMATTER);
     }
 
     /*

src/java.base/share/classes/java/util/jar/Manifest.java

@@ -336,7 +336,7 @@ public class Manifest implements Cloneable {
                     lastline = buf;
                     continue;
                 }
-                name = new String(buf, 0, buf.length, UTF_8.INSTANCE);
+                name = new String(buf, UTF_8.INSTANCE);
                 lastline = null;
             }
             Attributes attr = getAttributes(name);

src/java.desktop/share/classes/javax/swing/text/html/parser/Entity.java

@@ -114,7 +114,7 @@ class Entity implements DTDConstants {
      * @return the data as a <code>String</code>
      */
     public String getString() {
-        return new String(data, 0, data.length);
+        return new String(data);
     }
 
 

src/java.desktop/windows/classes/sun/awt/windows/WDataTransferer.java

@@ -241,7 +241,7 @@ final class WDataTransferer extends DataTransferer {
             if (bytes == null || !DataFlavor.javaFileListFlavor.equals(flavor)) {
                 throw new IOException("data translation failed");
             }
-            String st = new String(bytes, 0, bytes.length, UTF_16LE);
+            String st = new String(bytes, UTF_16LE);
             String[] filenames = st.split("\0");
             if( 0 == filenames.length ){
                 return null;

test/micro/org/openjdk/bench/java/lang/StringConstructor.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2018, 2022, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package micro.org.openjdk.bench.java.lang;
+
+import org.openjdk.jmh.annotations.*;
+
+import java.nio.charset.StandardCharsets;
+import java.util.concurrent.TimeUnit;
+
+@Fork(5)
+@State(Scope.Thread)
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@Warmup(iterations = 5, time = 5)
+@Measurement(iterations = 10, time = 5)
+public class StringConstructor {
+  private byte[] array;
+
+  @Setup
+  public void setup() {
+    array = "".getBytes(StandardCharsets.UTF_8);
+  }
+
+  @Benchmark
+  public String newStringFromArray() {
+    return new String(array);
+  }
+
+  @Benchmark
+  public String newStringFromArrayWithCharset() {
+    return new String(array, StandardCharsets.UTF_8);
+  }
+
+  @Benchmark
+  public String newStringFromArrayWithCharsetName() throws Exception {
+    return new String(array, StandardCharsets.UTF_8.name());
+  }
+
+  @Benchmark
+  public String newStringFromRangedArray() {
+    return new String(array, 0, 0);
+  }
+
+  @Benchmark
+  public String newStringFromRangedArrayWithCharset() {
+    return new String(array, 0, 0, StandardCharsets.UTF_8);
+  }
+
+  @Benchmark
+  public String newStringFromRangedArrayWithCharsetName() throws Exception {
+    return new String(array, 0, 0, StandardCharsets.UTF_8.name());
+  }
+}