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

*** 23,32 ****
--- 23,33 ----
   * questions.
   */
  
  package java.lang;
  
+ import sun.misc.ConstantLengthCharSequence;
  import sun.misc.FloatingDecimal;
  import java.util.Arrays;
  import java.util.Spliterator;
  import java.util.stream.IntStream;
  import java.util.stream.StreamSupport;
*** 458,471 ****
--- 459,486 ----
              return appendNull();
          if (s instanceof String)
              return this.append((String)s);
          if (s instanceof AbstractStringBuilder)
              return this.append((AbstractStringBuilder)s);
+         if (s instanceof ConstantLengthCharSequence)
+             return this.append((ConstantLengthCharSequence)s);
  
          return this.append(s, 0, s.length());
      }
  
+     /**
+      * @since 1.9
+      */
+     AbstractStringBuilder append(ConstantLengthCharSequence ccs) {
+         // assert ccs != null;
+         int len = ccs.length();
+         ensureCapacityInternal(count + len);
+         ccs.getChars(0, len, value, count);
+         count += len;
+         return this;
+     }
+ 
      private AbstractStringBuilder appendNull() {
          int c = count;
          ensureCapacityInternal(c + 4);
          final char[] value = this.value;
          value[c++] = 'n';
*** 513,524 ****
--- 528,543 ----
              throw new IndexOutOfBoundsException(
                  "start " + start + ", end " + end + ", s.length() "
                  + s.length());
          int len = end - start;
          ensureCapacityInternal(count + len);
+         if (s instanceof ConstantLengthCharSequence) {
+             ((ConstantLengthCharSequence)s).getChars(start, end, value, count);
+         } else {
              for (int i = start, j = count; i < end; i++, j++)
                  value[j] = s.charAt(i);
+         }
          count += len;
          return this;
      }
  
      /**
*** 1075,1088 ****
--- 1094,1125 ----
      public AbstractStringBuilder insert(int dstOffset, CharSequence s) {
          if (s == null)
              s = "null";
          if (s instanceof String)
              return this.insert(dstOffset, (String)s);
+         if (s instanceof ConstantLengthCharSequence)
+             return this.insert(dstOffset, (ConstantLengthCharSequence)s);
          return this.insert(dstOffset, s, 0, s.length());
      }
  
      /**
+      * @since 1.9
+      */
+     AbstractStringBuilder insert(int offset, ConstantLengthCharSequence ccs) {
+         if ((offset < 0) || (offset > length()))
+             throw new StringIndexOutOfBoundsException(offset);
+         if (ccs == null)
+             ccs = "null";
+         int len = ccs.length();
+         ensureCapacityInternal(count + len);
+         System.arraycopy(value, offset, value, offset + len, count - offset);
+         ccs.getChars(0, len, value, offset);
+         count += len;
+         return this;
+     }
+ 
+     /**
       * Inserts a subsequence of the specified {@code CharSequence} into
       * this sequence.
       * <p>
       * The subsequence of the argument {@code s} specified by
       * {@code start} and {@code end} are inserted,
*** 1136,1147 ****
                  + s.length());
          int len = end - start;
          ensureCapacityInternal(count + len);
          System.arraycopy(value, dstOffset, value, dstOffset + len,
                           count - dstOffset);
!         for (int i=start; i<end; i++)
              value[dstOffset++] = s.charAt(i);
          count += len;
          return this;
      }
  
      /**
--- 1173,1188 ----
                  + s.length());
          int len = end - start;
          ensureCapacityInternal(count + len);
          System.arraycopy(value, dstOffset, value, dstOffset + len,
                           count - dstOffset);
!         if (s instanceof ConstantLengthCharSequence) {
!             ((ConstantLengthCharSequence)s).getChars(start, end, value, dstOffset);
!         } else {
!             for (int i = start; i < end; i++)
                  value[dstOffset++] = s.charAt(i);
+         }
          count += len;
          return this;
      }
  
      /**