자료구조 해시 맵 처리하기

[주인장]

package data.process;

import java.io.File;

import java.io.FileNotFoundException;

import java.util.HashMap;

import java.util.Scanner;

public class HashMapProcess {

       public static void main(String[] args) {

             File dataFile = new File("datas/hashmap/Countries.dat");

//        System.out.println(dataFile.length());

             HashMap<String, Integer> dataSet = new HashMap<String, Integer>();

             try {

                    Scanner input = new Scanner(dataFile);

                    while (input.hasNext()) {

                           String country = input.next();

                           int population = input.nextInt();

                           dataSet.put(country, population);       // 해시에 데이터 입력

                    }

                    input.close();

             } catch (FileNotFoundException e) {

                    System.out.println(e);

             }

             System.out.printf("dataset.size(): %d\n", dataSet.size());

        System.out.printf("dataset.get(\"Peru\"): %,d\n", dataSet.get("Peru"));

        dataSet.put("Peru", 31000000);

        System.out.printf("dataset.size(): %d%n", dataSet.size());

        System.out.printf("dataset.get(\"Peru\"): %,d%n", dataSet.get("Peru"));

       }

}

>> 결과 

dataset.size(): 7
dataset.get("Peru"): 29,907,003
dataset.size(): 7
dataset.get("Peru"): 31,000,000