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how to compare two different <ArrayList>>String> objects for duplicates

Last Modified: 2013-11-23
For example, i have two different ArrayList objects

ArrayList<String> column1 = new ArrayList<String>();
ArrayList<String> column2 = new ArrayList<String>();

column1 object contains 200 text lines
column2 object contains 400 text lines

I would like to find out if each column1 text lines are duplicate in column2 text lines and save all un-duplicate text lines into a file.

Here's what I'm done so far:

                      for(String textLineA: columnA = h.get(getAllComboSelections[0]))
                                  Pattern columnA = Pattern.compile(textLineA);          
                                  Matcher matchM = columnA.matcher(textLineA);
                                         for(String textLineB: columnB = h.get(getAllComboSelections[0]))  
                                          Matcher matchM = columnB.matcher(textLineB);    

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