Summarization.java

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Summarization {
    public static String summarize(List<Item> items){
        StringBuilder sb = new StringBuilder();
        Map<String,Map<String,Integer>> headcount = new HashMap<>();
        int errorCount = 0;
        for(Item item: items){
            if(item.isError()){
                errorCount++;
            }
            else if(!headcount.containsKey(item.getName())){
                headcount.put(item.getName(),(new HashMap<>()));
                if(item.getName() == null){
                    headcount.get(null).put("-1",1);
                }
                else if(item.getPrice() == null){
                    headcount.get("error").put("-1",1);
                }
                else{
                    headcount.get(item.getName()).put(item.getPrice(),1);
                }
            }
            else{
                if(!headcount.get(item.getName()).containsKey(item.getPrice())){
                    headcount.get(item.getName()).put(item.getPrice(),1);
                }
                else if(item.getName() == null){
                    Integer temp = headcount.get(null).get("-1");
                    headcount.get(null).put("-1",temp + 1);

                }
                else if(item.getPrice() == null){
                    Integer temp = headcount.get("error").get("-1");
                    headcount.get("error").replace("-1",temp + 1);
                }
                else{
                    Integer temp = headcount.get(item.getName()).get(item.getPrice());
                    headcount.get(item.getName()).replace(item.getPrice(),temp + 1);
                }
            }
        }
        for(String name: headcount.keySet()){
            int total = 0;
            for(String price: headcount.get(name).keySet()){
                total+=headcount.get(name).get(price);
            }
            sb.append(String.format("name:%4s \t \t seen: %s times\n",name,total));
            sb.append("============= \t \t =============\n");
            for(String price: headcount.get(name).keySet()){
                sb.append(String.format("Price:%4s \t \t seen: %s times\n",price,headcount.get(name).get(price)));
                sb.append("-------------\t\t -------------\n");
            }
            sb.append("\n");
        }
        sb.append(String.format("Errors \t \t seen: %s times",errorCount));
        return sb.toString();
    }
}