@Override
		public int execute(StringBuilder buf) {
			buf.append(text);
			if ( tokens.get(index).getType()!=Token.EOF ) {
				buf.append(tokens.get(index).getText());
			}
			return index+1;
		}
Execute the rewrite operation by possibly adding to the buffer.
 Return the index of the next token to operate on.
runtime/Java/src/org/antlr/v4/runtime/TokenStreamRewriter.java