docs: public void addElements(final int index, final char a[], final int offset, final int length) {
          ensureIndex(index);
          CharArrays.ensureOffsetLength(a, offset, length);
          grow(size + length);
          System.arraycopy(this.a, index, this.a, index + length, size - index);
          System.arraycopy(a, offset, this.a, index, length);
          size += length;
      }