diff --git a/user/super/com/google/gwt/emul/java/lang/AbstractStringBuilder.java b/user/super/com/google/gwt/emul/java/lang/AbstractStringBuilder.java
index 40c3819..4aec949 100644
--- a/user/super/com/google/gwt/emul/java/lang/AbstractStringBuilder.java
+++ b/user/super/com/google/gwt/emul/java/lang/AbstractStringBuilder.java
@@ -15,8 +15,6 @@
  */
 package java.lang;
 
-import static javaemul.internal.InternalPreconditions.checkStringBounds;
-
 /**
  * A base class to share implementation between {@link StringBuffer} and {@link StringBuilder}.
  * <p>
@@ -63,11 +61,7 @@
   }
 
   public void getChars(int srcStart, int srcEnd, char[] dst, int dstStart) {
-    checkStringBounds(srcStart, srcEnd, length());
-    checkStringBounds(dstStart, dstStart + (srcEnd - srcStart), dst.length);
-    while (srcStart < srcEnd) {
-      dst[dstStart++] = string.charAt(srcStart++);
-    }
+    string.getChars(srcStart, srcEnd, dst, dstStart);
   }
 
   /**
diff --git a/user/super/com/google/gwt/emul/java/lang/String.java b/user/super/com/google/gwt/emul/java/lang/String.java
index 18e1a5b..3b28b4e 100644
--- a/user/super/com/google/gwt/emul/java/lang/String.java
+++ b/user/super/com/google/gwt/emul/java/lang/String.java
@@ -16,7 +16,7 @@
 
 package java.lang;
 
-import static javaemul.internal.InternalPreconditions.checkStringBounds;
+import static javaemul.internal.InternalPreconditions.checkCriticalStringBounds;
 
 import java.io.Serializable;
 import java.io.UnsupportedEncodingException;
@@ -137,7 +137,7 @@
 
   public static String valueOf(char x[], int offset, int count) {
     int end = offset + count;
-    checkStringBounds(offset, end, x.length);
+    checkCriticalStringBounds(offset, end, x.length);
     // Work around function.prototype.apply call stack size limits:
     // https://code.google.com/p/v8/issues/detail?id=2896
     // Performance: http://jsperf.com/string-fromcharcode-test/13
@@ -448,8 +448,11 @@
   }
 
   public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin) {
-    for (int srcIdx = srcBegin; srcIdx < srcEnd; ++srcIdx) {
-      dst[dstBegin++] = charAt(srcIdx);
+    checkCriticalStringBounds(srcBegin, srcEnd, length());
+    checkCriticalStringBounds(dstBegin, dstBegin + (srcEnd - srcBegin), dst.length);
+
+    while (srcBegin < srcEnd) {
+      dst[dstBegin++] = charAt(srcBegin++);
     }
   }
 
diff --git a/user/super/com/google/gwt/emul/javaemul/internal/InternalPreconditions.java b/user/super/com/google/gwt/emul/javaemul/internal/InternalPreconditions.java
index ff5f30b..f47a491 100644
--- a/user/super/com/google/gwt/emul/javaemul/internal/InternalPreconditions.java
+++ b/user/super/com/google/gwt/emul/javaemul/internal/InternalPreconditions.java
@@ -441,7 +441,7 @@
   }
 
   /**
-   * Ensures that {@code index} specifies a valid <i>element</i> in an array, list or string of size
+   * Ensures that {@code index} specifies a valid <i>element</i> in a list or string of size
    * {@code size}. An element index may range from zero, inclusive, to {@code size}, exclusive.
    */
   public static void checkElementIndex(int index, int size) {
@@ -463,7 +463,7 @@
   }
 
   /**
-   * Ensures that {@code index} specifies a valid <i>position</i> in an array, list or string of
+   * Ensures that {@code index} specifies a valid <i>position</i> in a list of
    * size {@code size}. A position index may range from zero to {@code size}, inclusive.
    */
   public static void checkPositionIndex(int index, int size) {
@@ -485,8 +485,8 @@
   }
 
   /**
-   * Ensures that {@code start} and {@code end} specify a valid <i>positions</i> in an array, list
-   * or string of size {@code size}, and are in order. A position index may range from zero to
+   * Ensures that {@code start} and {@code end} specify a valid <i>positions</i> in a list
+   * of size {@code size}, and are in order. A position index may range from zero to
    * {@code size}, inclusive.
    */
   public static void checkPositionIndexes(int start, int end, int size) {
@@ -502,16 +502,14 @@
   }
 
   /**
-   * Ensures that {@code start} and {@code end} specify a valid <i>positions</i> in an array, list
-   * or string of size {@code size}, and are in order. A position index may range from zero to
+   * Ensures that {@code start} and {@code end} specify a valid <i>positions</i> in a list
+   * of size {@code size}, and are in order. A position index may range from zero to
    * {@code size}, inclusive.
    */
   public static void checkCriticalPositionIndexes(int start, int end, int size) {
-    if (start < 0) {
-      throw new IndexOutOfBoundsException("fromIndex: " + start + " < 0");
-    }
-    if (end > size) {
-      throw new IndexOutOfBoundsException("toIndex: " + end + " > size " + size);
+    if (start < 0 || end > size) {
+      throw new IndexOutOfBoundsException(
+          "fromIndex: " + start + ", toIndex: " + end + ", size: " + size);
     }
     if (start > end) {
       throw new IllegalArgumentException("fromIndex: " + start + " > toIndex: " + end);
@@ -519,36 +517,30 @@
   }
 
   /**
-   * Checks that bounds are correct.
+   * Checks that array bounds are correct.
    *
+   * @throws IllegalArgumentException if {@code start > end}
    * @throws ArrayIndexOutOfBoundsException if the range is not legal
    */
   public static void checkCriticalArrayBounds(int start, int end, int length) {
     if (start > end) {
       throw new IllegalArgumentException("fromIndex: " + start + " > toIndex: " + end);
     }
-    if (start < 0) {
-      throw new ArrayIndexOutOfBoundsException("fromIndex: " + start + " < 0");
-    }
-    if (end > length) {
-      throw new ArrayIndexOutOfBoundsException("toIndex: " + end + " > length " + length);
+    if (start < 0 || end > length) {
+      throw new ArrayIndexOutOfBoundsException(
+          "fromIndex: " + start + ", toIndex: " + end + ", length: " + length);
     }
   }
 
   /**
-   * Checks that bounds are correct.
+   * Checks that string bounds are correct.
    *
    * @throws StringIndexOutOfBoundsException if the range is not legal
    */
-  public static void checkStringBounds(int start, int end, int size) {
-    if (start < 0) {
-      throw new StringIndexOutOfBoundsException("fromIndex: " + start + " < 0");
-    }
-    if (end > size) {
-      throw new StringIndexOutOfBoundsException("toIndex: " + end + " > size " + size);
-    }
-    if (end < start) {
-      throw new StringIndexOutOfBoundsException("fromIndex: " + start + " > toIndex: " + end);
+  public static void checkCriticalStringBounds(int start, int end, int length) {
+    if (start < 0 || end > length || end < start) {
+      throw new StringIndexOutOfBoundsException(
+          "fromIndex: " + start + ", toIndex: " + end + ", length: " + length);
     }
   }