자바 Map

개요

Map 컬렉션 클래스들은 키와 값을 하나의 쌍으로 저장하는 방식(key-value 방식)을 사용

key 중복 허용 X, value 중복 허용 O

• 사용 예제

import java.util.HashMap;
public class Main {
  public static void main(String[] args) {
    HashMap<String, String> capitalCities = new HashMap<String, String>();
    capitalCities.put("England", "London");
    capitalCities.put("Germany", "Berlin");
    capitalCities.put("Norway", "Oslo");
    System.out.println(capitalCities);
  }
}

import java.util.HashMap;
public class Main {
  public static void main(String[] args) {
    HashMap<String, String> capitalCities = new HashMap<String, String>();
    capitalCities.put("England", "London");
    capitalCities.put("Germany", "Berlin");
    capitalCities.put("Norway", "Oslo");
    for (String i : capitalCities.keySet()) {
      System.out.println(i);
    }
  }
}

import java.util.HashMap;
public class Main {
  public static void main(String[] args) {
    HashMap<String, String> capitalCities = new HashMap<String, String>();
    capitalCities.put("England", "London");
    capitalCities.put("Germany", "Berlin");
    capitalCities.put("Norway", "Oslo");
   for (String i : capitalCities.values()) {
     System.out.println(i);
   }
  }
}

import java.util.HashMap;
public class Main {
  public static void main(String[] args) {
    HashMap<String, String> capitalCities = new HashMap<String, String>();
    capitalCities.put("England", "London");
    capitalCities.put("Germany", "Berlin");
    capitalCities.put("Norway", "Oslo");
   for (String i : capitalCities.keySet()) {
     System.out.println("key: " + i + " value: " + capitalCities.get(i));
   }
  }
}