HashMap usage in Java

[neo_2010]

Hi Everybody,
I made a small sample about using HashMaps in Java ,and i hope to be useful to everyone what to know how to manipulate with it.

/**
 * @author 	: Mohamed Saleh AbdEl-Aziz
 */
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
 
public class HashListSample {
 
    private Map<Integer, Integer> intMap;
    private Map<String, String> strMap;
    private Map<Integer, Boolean> boolMap;
    private Map<Integer, ArrayList> arrListMap;
 
    public HashListSample() {
        intMap = new HashMap<Integer, Integer>();
        strMap = new HashMap<String, String>();
        boolMap = new HashMap<Integer, Boolean>();
        arrListMap = new HashMap<Integer, ArrayList>();
 
        fillBoolMap();
        fillIntMap();
        fillStrMap();
    }
 
    public void fillArrayList() {
        ArrayList<String> objStrArrList = null;
        ArrayList<Byte> objBytArrList = null;
 
        objStrArrList.add("Hello");
        objStrArrList.add("World");
 
        objBytArrList.add(Byte.valueOf("12"));
        objBytArrList.add(Byte.valueOf("78"));
 
        arrListMap.put(3333, objStrArrList);
        arrListMap.put(5555, objBytArrList);
 
 
    }
 
    public void fillIntMap() {
        Integer myIntValues[] = new Integer[]{45, 666, 9778, 14522, 31011, 78};
        Integer myIntKeys[] = new Integer[]{1, 2, 33, 4, 5, 66};
 
        for (int x = 0; x < myIntValues.length; x++) {
            intMap.put(myIntKeys[x], myIntValues[x]);
        }
        System.out.println("Integer Map has been filled...");
    }
 
    public void fillStrMap() {
        String myStrValues[] = new String[]{"Mohamed", "Saleh", "Java Junior Developer"};
        String myStrKeys[] = new String[]{"FN", "MD", "Job"};
 
        for (int x = 0; x < myStrValues.length; x++) {
            strMap.put(myStrKeys[x], myStrValues[x]);
        }
        System.out.println("String Map has been filled...");
    }
 
    public void fillBoolMap() {
 
        Integer myBoolKeys[] = new Integer[]{1, 11, 111, 0};
        Boolean myBoolValues[] = new Boolean[]{true, true, true, false};
 
        for (int x = 0; x < myBoolValues.length; x++) {
            boolMap.put(myBoolKeys[x], myBoolValues[x]);
        }
        System.out.println("Boolean Map has been filled...");
    }
 
    public void doSomeOperations() {
        //Remove item from Map is depend on the Key value....
 
        System.out.println();
        System.out.println("Remove item from Integer Map...");
        intMap.remove((Integer) 4);
 
        System.out.println();
        System.out.println("Remove item from Boolean Map...");
        boolMap.remove((Integer) 0);
 
        System.out.println();
        System.out.println("Remove item from String Map...");
        strMap.remove((String) "MN");
 
    }
 
    public void clearAllMap() {
        System.out.println();
        System.out.println("Clear all Maps Objects....");
        intMap.clear();
        boolMap.clear();
        strMap.clear();
    }
 
    public void viewAllInfo() {
        /**********************************************************************/
        System.out.println("Ineger Map size: " + intMap.size());
        System.out.println("Boolean Map size: " + boolMap.size());
        System.out.println("String Map size: " + strMap.size());
        System.out.println();
        /**********************************************************************/
        //Map DataStructure is getting Data Depend on the key of your Item.
        System.out.println("View Some of Integer Map Values...");
        System.out.println("Item key is {66} in Ineger Map is :" + intMap.get((Integer) 66));
        System.out.println("Item key is {4} in Ineger Map is :" + intMap.get((Integer) 4));
        System.out.println();
 
        System.out.println("View Some of Boolean Map Values...");
        System.out.println("Item key is {1} in Boolean Map is :" + boolMap.get((Integer) 1));
        System.out.println("Item key is {0} in Boolean Map is :" + boolMap.get((Integer) 0));
        System.out.println();
 
        System.out.println("View Some of String Map Values...");
        System.out.println("Item key is {FN} in String Map is :" + strMap.get((String) "FN"));
        System.out.println("Item key is {Job} in String Map is :" + strMap.get((String) "Job"));
 
    }
 
    public static void main(String args[]) {
        HashListSample cls = new HashListSample();
        cls.viewAllInfo();
        cls.doSomeOperations();
        cls.viewAllInfo();
        cls.clearAllMap();
        cls.viewAllInfo();
    }
}

[chronoz13]

is this a sample program exercise?
i think your should post it in 'java tips and tutorials'

[Json]

You should write a little example where you use your own created object as a key where you override equals and hashCode

// Json