In today's example I will show you how to add multiple values to a key in a HashMap or Hashtable.
The key is to add the values in an ArrayList everytime.
Check out the next example for more :
/*
* @(#)HashMapMultipleValues.java 1.1 03/05/09
*
* Copyright 2009 Lazy Coder. All rights reserved.
* To be used only for educational purposes.
* Not to be reproduced and published
* without seeking prior consent.
*/
package com.lazy.coder.examples;
import java.util.ArrayList;
import java.util.HashMap;
/**
* @author lazycoder
*
*/
public class HashMapMultipleValues {
public static void addMultipleValues(HashMap map,
Object key, Object value){
Object prevValue = map.get(key);
ArrayList valueList;
if( prevValue == null ){
valueList = new ArrayList();
map.put(key, valueList);
}else{
valueList = (ArrayList)prevValue;
}
valueList.add(value);
}
/**
* @param args
*/
public static void main(String[] args) {
HashMap map = new HashMap();
String key = "LazyCoder";
addMultipleValues(map, key, "LazyCoder");
addMultipleValues(map, key, "is");
addMultipleValues(map, key, "Lazy");
ArrayList valuesList = (ArrayList)map.get(key);
for(Object value : valuesList){
System.out.println(value);
}
}
}
If done normally like this :
map.put(key, "LazyCoder");
map.put(key, "is");
map.put(key, "Lazy");
the old value gets overriden with the latest value put against the key in the HashMap
in this case "Lazy" will be saved against the key in map.
LazyCoder
Signing off for now...
