@Override
		public String toString() {
			String opName = getClass().getName();
			int $index = opName.indexOf('$');
			opName = opName.substring($index+1, opName.length());
			return "<"+opName+"@"+tokens.get(index)+
					":\""+text+"\">";
		}
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