HashMap class with generics

msi_333 · **Posted:** Mon Dec 28, 2009 7:58 pm

HashMap class with generics :
In this example . we see how we reverse the key and value .

Code:

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

public class TestHashMap {

    public static void main(String args[])
    {
    
    TestHashMap hashMap = new TestHashMap();
    
    HashMap<String,Integer> oldhashMap = new HashMap<String, Integer>();
    oldhashMap.put("a",1);
    oldhashMap.put("2", 2);
    
    HashMap<Integer,String>  map = hashMap.copyHashMap(oldhashMap);
    System.out.println("Value of key =1 is : "+map.get(1));
    
    }
    
    public <V, K> HashMap<V, K> copyHashMap(HashMap<K,V> oldhashMap)
    {
    HashMap<V, K> newhashMap = new HashMap<V,K>();
    
    for(Map.Entry<K, V> entry :oldhashMap.entrySet())
    {
        newhashMap.put(entry.getValue(),entry.getKey());
    }
    
    return  newhashMap;
    }
}
 

The output is :
Value of key =1 is : a

HashMap class with generics

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