test.java

package sha1;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;
import java.util.stream.Collectors;

import static java.util.stream.Collectors.groupingBy;

public class Main {

    public static void main(String[] args) throws IOException {

        List<Bank> bankList = new ArrayList() {{
            add(new Bank("Bank500", 500));
            add(new Bank("Bank100", 100));
            add(new Bank("Bank50", 50));
            add(new Bank("Bank20", 20));
            add(new Bank("Coin10", 10));
            add(new Bank("Coin5", 5));
            add(new Bank("Coin1", 1));
        }};

        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Enter GrandTotal:");
        Integer grandTotal = Integer.valueOf(reader.readLine());
        System.out.print("Enter RecvMoney:");
        Integer rev = Integer.valueOf(reader.readLine());

        if (rev - grandTotal > 0) {
            List<Bank> sumValue = new ArrayList<>();
            int moneyChange = rev - grandTotal;
            while (moneyChange > sumStack(sumValue)) {
                Optional<Bank> found = bankList.stream().filter(v -> v.getValue() <= (moneyChange - sumStack(sumValue))).findFirst();
                if (found.isPresent()) {
                    sumValue.add(found.get());
                } else {
                    break;
                }
            }
            String stackStr = mapResult(sumValue);

            System.out.println("[" + stackStr + "]");
        }
    }

    private static String mapResult(List<Bank> sumValue) {
        Map<String, List<Bank>> grouped = sumValue
                .stream()
                .collect(groupingBy(Bank::getBankName));
        Set<String> keys = grouped.keySet();
        Set<Bank> returnList = new HashSet<>();
        for (String key : keys) {
            returnList.add(new Bank(key, grouped.get(key).size()));
        }
        return returnList
                .stream()
                .map(v -> "{\"" + v.getBankName() + "\": \"" + v.getValue() + "\"}")
                .collect(Collectors.joining(", "));
    }

    private static Integer sumStack(List<Bank> sumValue) {
        return sumValue.stream().map(Bank::getValue).reduce(0, Integer::sum);
    }

    public static class Bank {
        private String bankName;
        private Integer value;

        Bank(String name, Integer val) {
            this.bankName = name;
            this.value = val;
        }

        public String getBankName() {
            return bankName;
        }

        public Integer getValue() {
            return this.value;
        }

    }

}