Collection framework - HashMap

 

 

HashMap<key,value>

 

• HashMap is not thread-safe which allows you faster speed than HashTable.
• HashMap doesn't allow insertion order. *Use LinkedHashMap to preserve the fixed order.
• key doesn't allow duplicate key, but for value, duplication is allowed.

 

 

 

put() - key, value map에 입력

get() - key를 전달해야 그 key의 value가 반환된다. 

remove() - 해당 key의 key와 value 삭제

 

 

 

Example Code

import java.util.*;
 
public class Main {
    public static void main(String[] args) {
        String[] fruit = {"apple", "banana", "cherry"};
        Map<Integer,String> hash = new HashMap<>();
 
        for (int i = 0; i < fruit.length; i++) {
            hash.put(i,fruit[i]); //auto-boxing
        }
        
        hash.put(0,"kiwi");
        
        System.out.println(hash.get(0)); //kiwi
        System.out.println(hash.get(1)); //banana
        System.out.println(hash.get(2)); //cherry
 
        hash.remove(0);
 
        System.out.println(hash.get(0)); //null
 
    }
}