AmpleMarket.Java

public class AmpleMarket {
    
    public static void main(String[] args) {
        String mainString = "hi {!first name}";
        HashMap<String,String> patternDictonary = new HashMap<>();
        patternDictonary.put("first name","prashant");
        populateTemplate(mainString, patternDictonary);
    }

    private static void populateTemplate(String mainString, HashMap patternDictonary) {
        for (Object key : patternDictonary.keySet()) {
            String singleKey = "{!"+key+"}";
            if(mainString.contains(singleKey)){
                mainString = mainString.replace(singleKey, (CharSequence) patternDictonary.get(key));
            }
        }
        System.out.println(mainString);
    }

}