Improve JavaDoc

Co-authored-by: Chen Liang <liach@openjdk.org>

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

@@ -530,12 +530,7 @@ abstract sealed class AbstractStringBuilder implements Appendable, CharSequence
     }
 
     /**
-     * Returns the number of Unicode code points in
-     * this sequence. Unpaired surrogates count
-     * as one code point each.
-     *
-     * @return the number of Unicode code points in this String
-     * @since  26
+     * @since 27
      */
     public int codePointCount() {
         byte coder = this.coder;

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

@@ -254,12 +254,10 @@ public interface CharSequence {
     }
 
     /**
-     * Returns the number of Unicode code points in
-     * this sequence. Unpaired surrogates count
-     * as one code point each.
+     * {@return the number of Unicode code points in this character sequence}
+     * Unpaired surrogates count as one code point each.
      *
-     * @return the number of Unicode code points in this sequence
-     * @since 26
+     * @since 27
      */
     public default int codePointCount() {
         final int length = length();

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

@@ -10000,14 +10000,12 @@ class Character implements java.io.Serializable, Comparable<Character>, Constabl
     }
 
     /**
-     * Returns the number of Unicode code points in the
-     * {@code char} array argument. Unpaired
-     * surrogates count as one code point each.
+     * {@return the number of Unicode code points in the {@code char} array}
+     * Unpaired surrogates count as one code point each.
      *
      * @param a the {@code char} array
-     * @return the number of Unicode code points in the char array
-     * @throws NullPointerException if {@code a} is null.
-     * @since  26
+     * @throws NullPointerException if {@code a} is null
+     * @since 27
      */
     public static int codePointCount(char[] a) {
         return codePointCountImpl(a, 0, a.length);

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

@@ -1715,12 +1715,10 @@ public final class String
     }
 
     /**
-     * Returns the number of Unicode code points in
-     * this {@code String}. Unpaired surrogates count
-     * as one code point each.
+     * {@return the number of Unicode code points in this String}
+     * Unpaired surrogates count as one code point each.
      *
-     * @return the number of Unicode code points in this String
-     * @since  26
+     * @since 27
      */
     public int codePointCount() {
         if (isLatin1()) {

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

@@ -271,7 +271,7 @@ import jdk.internal.vm.annotation.IntrinsicCandidate;
     }
 
     /**
-     * @since     26
+     * @since 27
      */
     @Override
     public synchronized int codePointCount() {