Using a HashMap in Java

After using the ArrayList mentioned in my last post, I thought to see what the HashMap is all about. Once defined, the HashMap takes a "key" and a "value". In the code snippet below, the "1" is the key and the "JAN" is the value.

These are used within database code where within a table, there will be a key in one column and a value in the other column. Not being into extreme database programming that would require the use of a key/value, thought it would be useful to at least understand how to code these. 

ArrayFunction1() was coded to put the key/value into myHashMap.
ArrayFunction2() was coded to extract various items from myHashMap.

If this looks familiar, it is a direct copy of the ArrayList() in the previous post as well. Found it very convenient were all that was needed was a search/replace operation.

public static HashMap <Integer, String> ArrayFunction1 () {   
   HashMap<Integer, String> myHashMap = new HashMap<Integer, String>();
   Logger("ArrayFunction1: Entry");
...
   myHashMap.put(1,"JAN");
   myHashMap.put(2,"FEB");
   myHashMap.put(3,"MAR");
   myHashMap.put(4,"APR");
...
   Logger("ArrayFunction1: Exit");
}

public static void ArrayFunction2 (HashMap<Integer,  String> myinputarray) {
   Logger("ArrayFunction2: Entry");
...
   Logger("ArrayFunction2: keySet:        " + myinputarray.keySet());          
   Logger("ArrayFunction2: entrySet:     " + myinputarray.entrySet());   
   Logger("ArrayFunction2: values:        " + myinputarray.values());
...
   Logger("ArrayFunction2: Exit");
}

And this is the output. It shows the keySet(), and entrySet() and the values() that are in the HashMap. I left out some of the boolean methods (containsValue()), containsKey()). They work pretty cool, showing true or false if the item is present in either the key or value.

ArrayFunction2: keySet:        [1, 2, 3, 4]
ArrayFunction2: entrySet:     [1=JAN, 2=FEB, 3=MAR, 4=APR]
ArrayFunction2: values:        [JAN, FEB, MAR, APR]

Wondering what that Logger() function is? It is that method shown in the previous post that accepts a String as the only argument and simply outputs the input string to stdout. In otherwords, Logger() is a just wrapper to System.out.println().