src/share/classes/java/util/StringJoiner.java

rev 7571 : 8017231: Add StringJoiner.merge
Reviewed-by:
Contributed-by: brian.goetz@oracle.com, henry.jen@oracle.com

*** 112,122 ****
       * @param  prefix the sequence of characters to be used at the beginning
       * @param  suffix the sequence of characters to be used at the end
       * @throws NullPointerException if {@code prefix}, {@code delimiter}, or
       *         {@code suffix} is {@code null}
       */
!     public StringJoiner(CharSequence delimiter, CharSequence prefix,
              CharSequence suffix) {
          Objects.requireNonNull(prefix, "The prefix must not be null");
          Objects.requireNonNull(delimiter, "The delimiter must not be null");
          Objects.requireNonNull(suffix, "The suffix must not be null");
          // make defensive copies of arguments
--- 112,123 ----
       * @param  prefix the sequence of characters to be used at the beginning
       * @param  suffix the sequence of characters to be used at the end
       * @throws NullPointerException if {@code prefix}, {@code delimiter}, or
       *         {@code suffix} is {@code null}
       */
!     public StringJoiner(CharSequence delimiter,
!                         CharSequence prefix,
                          CharSequence suffix) {
          Objects.requireNonNull(prefix, "The prefix must not be null");
          Objects.requireNonNull(delimiter, "The delimiter must not be null");
          Objects.requireNonNull(suffix, "The suffix must not be null");
          // make defensive copies of arguments
*** 170,180 ****
              }
          }
      }
  
      /**
!      * Add the a copy of the supplied {@code CharSequence} value as the next
       * element of the {@code StringJoiner} value. If {@code newElement} is
       * {@code null}, then {@code "null"} is added.
       *
       * @param  newElement The element to add
       * @return a reference to this {@code StringJoiner}
--- 171,181 ----
              }
          }
      }
  
      /**
!      * Adds a copy of the given {@code CharSequence} value as the next
       * element of the {@code StringJoiner} value. If {@code newElement} is
       * {@code null}, then {@code "null"} is added.
       *
       * @param  newElement The element to add
       * @return a reference to this {@code StringJoiner}
*** 182,191 ****
--- 183,222 ----
      public StringJoiner add(CharSequence newElement) {
          prepareBuilder().append(newElement);
          return this;
      }
  
+     /**
+      * Adds the contents of the given {@code StringJoiner} without prefix and
+      * suffix as the next element if it is non-empty. If the given {@code
+      * StringJoiner} is empty, the call has no effect.
+      *
+      * <p>A {@code StringJoiner} is empty if {@link #add(CharSequence) add()}
+      * has never been called, and if {@code merge()} has never been called
+      * with a non-empty {@code StringJoiner} argument.
+      *
+      * <p>If the other {@code StringJoiner} is using a different delimiter,
+      * then elements from the other {@code StringJoiner} are concatenated with
+      * that delimiter and the result is appended to this {@code StringJoiner}
+      * as a single element.
+      *
+      * @param other The {@code StringJoiner} whose contents should be merged
+      *              into this one
+      * @throws NullPointerException if the other {@code StringJoiner} is null
+      */
+     public StringJoiner merge(StringJoiner other) {
+         Objects.requireNonNull(other);
+         if (other.value != null) {
+             StringBuilder builder = prepareBuilder();
+             StringBuilder otherBuilder = other.value;
+             if (other.prefix.length() < otherBuilder.length()) {
+                 builder.append(otherBuilder, other.prefix.length(), otherBuilder.length());
+             }
+         }
+         return this;
+     }
+ 
      private StringBuilder prepareBuilder() {
          if (value != null) {
              value.append(delimiter);
          } else {
              value = new StringBuilder().append(prefix);