adding multiple entries to a HashMap at once in one statement

Question

I need to initialize a constant HashMap and would like to do it in one line statement. Avoiding sth like this:

  hashMap.put(\"One\", new Integer(1)); // add         


        

Answer 1

Another approach may be writing special function to extract all elements values from one string by regular-expression:

import java.util.HashMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Example {
    public static void main (String[] args){
        HashMap hashMapStringInteger = createHashMapStringIntegerInOneStat("'one' => '1', 'two' => '2' , 'three'=>'3'  ");

        System.out.println(hashMapStringInteger); // {one=1, two=2, three=3}
    }

    private static HashMap createHashMapStringIntegerInOneStat(String str) {
        HashMap returnVar = new HashMap();

        String currentStr = str;
        Pattern pattern1 = Pattern.compile("^\\s*'([^']*)'\\s*=\\s*>\\s*'([^']*)'\\s*,?\\s*(.*)$");

        // Parse all elements in the given string.
        boolean thereIsMore = true;
        while (thereIsMore){
            Matcher matcher = pattern1.matcher(currentStr);
            if (matcher.find()) {
                returnVar.put(matcher.group(1),Integer.valueOf(matcher.group(2)));
                currentStr = matcher.group(3);
            }
            else{
                thereIsMore = false;
            }
        }

        // Validate that all elements in the given string were parsed properly
        if (currentStr.length() > 0){
            System.out.println("WARNING: Problematic string format. given String: " + str);
        }

        return returnVar;
    }
}