import java.util.*;
import java.lang.*;
import java.io.*;

class Ideone
{
   public static void main(String[] args)
   {
		Map<String, List<String>> masterList = new HashMap<String, List<String>>();
		List<String> finalPNList = new ArrayList<String>();
		List<String> modifier = new ArrayList<String>();
		List<String> skipped = new ArrayList<String>();
		masterList.put("A", Arrays.asList("123","123","456"));
		masterList.put("B", Arrays.asList("123","789","789"));
		for (Map.Entry<String, List<String>> e : masterList.entrySet()) {
		    String key = e.getKey();
		    List<String> val = e.getValue();
		    System.out.println(modifier.size());
		    for (String s : val) {
		        if (modifier.isEmpty())
		            finalPNList.add(s);
		        else if (!modifier.isEmpty() && masterList.get("A").contains(s)) {
		            // s has been added by parent process so SKIP!
		            skipped.add(s);
		        } else
		            finalPNList.add(s);    
		    }    
		    modifier.add(key);
		}
		System.out.println(finalPNList);
   }
}

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