Initializing HashMap in Java

Map<String,String> paramMap = new HashMap<>();

I tried to use HashMap when I read a list of numbers from csv and want to proceed to the next process only for unique ones, but ...

Map<String, String> paramMap = null; while((record = reader.readNext()) != null){ if(paramMap.get(record[0]) != null { continue; } paramMap.put(record[0],record[0]); Next processing }

Then, an error occurs in nullpointer.exception in the part of paramMap.get It's easy to know what to do

Map<String, String> paramMap = null;

With this, pramMap has not been initialized, and if you call it, a null reference will occur. Here

Map<String,String> paramMap = new HashMap<>();

Then it works fine

I would be grateful if you could tell me if there is another good way to retrieve unique records ^ _ ^

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