can someone give me example of what this means

Define the addSortedData method such that it adds the dataAdd argument to the list in the proper sorted location according to ticker symbol. If a company is already in the list with this ticker symbol, it is not added. There can only be one of each company in this list.

public void addSortedData(DJIACompany dataAdd)
//codes here

Don't do it like that.
Rather store the quote information in a Map, using the ticker symbol as the key.