Convert Map, HashMap or List/ArrayList to XML and reverse

HashMapToStringXml.java

package pritom;

import java.beans.XMLDecoder;
import java.beans.XMLEncoder;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Created by pritom on 5/05/14.
 */
public class HashMapToStringXml {
    public static void main(String[] args) {
        Map<Object, Object> hashMap = new HashMap<Object, Object>();
        hashMap.put("firstName", "Pritom");
        hashMap.put("lastName", "Kumar");

        Map<Object, Object> secondMap = new HashMap<Object, Object>();
        secondMap.put("timeIn", "8:00");
        secondMap.put("timeOut", "5:00");
        hashMap.put("timing", secondMap);

        List<Object> list = new ArrayList<Object>();
        list.add(20);
        list.add(30);
        list.add(40);
        list.add(secondMap);
        hashMap.put("contents", list);

        /* Map to XML and reverse */
        String mapToString = objectToString(hashMap);
        Map parsedMap = (Map) stringToObject(mapToString);
        System.out.println("Map to XML: \n" + mapToString + "\nXML to map:\n" + parsedMap);

        /* List to XML and reverse */
        String listToString = objectToString(list);
        List parsedList = (List) stringToObject(listToString);
        System.out.println("List to XML: \n" + listToString + "\nXML to list:\n" + parsedList);
    }

    public static String objectToString(Object hashMap) {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        XMLEncoder xmlEncoder = new XMLEncoder(bos);
        xmlEncoder.writeObject(hashMap);
        xmlEncoder.close();
        return bos.toString();
    }

    public static Object stringToObject(String string) {
        XMLDecoder xmlDecoder = new XMLDecoder(new ByteArrayInputStream(string.getBytes()));
        return xmlDecoder.readObject();
    }
}

Output

Map to XML: 
<?xml version="1.0" encoding="UTF-8"?>
<java version="1.7.0_45" class="java.beans.XMLDecoder">
 <object class="java.util.HashMap">
  <void method="put">
   <string>lastName</string>
   <string>Kumar</string>
  </void>
  <void method="put">
   <string>contents</string>
   <object class="java.util.ArrayList">
    <void method="add">
     <int>20</int>
    </void>
    <void method="add">
     <int>30</int>
    </void>
    <void method="add">
     <int>40</int>
    </void>
    <void method="add">
     <object class="java.util.HashMap" id="HashMap0">
      <void method="put">
       <string>timeOut</string>
       <string>5:00</string>
      </void>
      <void method="put">
       <string>timeIn</string>
       <string>8:00</string>
      </void>
     </object>
    </void>
   </object>
  </void>
  <void method="put">
   <string>timing</string>
   <object idref="HashMap0"/>
  </void>
  <void method="put">
   <string>firstName</string>
   <string>Pritom</string>
  </void>
 </object>
</java>

XML to map:
{
    lastName=Kumar, 
    contents=[
        20, 
        30, 
        40, 
        {
            timeOut=5:00, 
            timeIn=8:00
        }
    ], 
    firstName=Pritom, 
    timing={
        timeOut=5:00, 
        timeIn=8:00
    }
}



List to XML: 
<?xml version="1.0" encoding="UTF-8"?>
<java version="1.7.0_45" class="java.beans.XMLDecoder">
 <object class="java.util.ArrayList">
  <void method="add">
   <int>20</int>
  </void>
  <void method="add">
   <int>30</int>
  </void>
  <void method="add">
   <int>40</int>
  </void>
  <void method="add">
   <object class="java.util.HashMap">
    <void method="put">
     <string>timeOut</string>
     <string>5:00</string>
    </void>
    <void method="put">
     <string>timeIn</string>
     <string>8:00</string>
    </void>
   </object>
  </void>
 </object>
</java>

XML to list:
[20, 30, 40, {timeOut=5:00, timeIn=8:00}]

Sort an ArrayList base on multiple attributes using java/grails

I have an ArrayList of object. The object contain attributes name and classValue. So I want to sort the objects on the classValue, and for all objects in the same classValue I want to sort them on name.

---

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;

/**
 *
 * @author Pritom Kumar
 */
public class MapSort {
    public static void main(String[] args) {
        MapSort mapSort = new MapSort();
        mapSort.sort();
    }
    
    public void sort() {
        List keys = new ArrayList();
        HashMap map1 = new HashMap();
        map1.put("name", "Pritom");
        map1.put("classValue", 5);
        keys.add(map1);
        
        HashMap map2 = new HashMap();
        map2.put("name", "Bappi Lahiri");
        map2.put("classValue", 10);
        keys.add(map2);
        
        HashMap map3 = new HashMap();
        map3.put("name", "Ashok Kumar");
        map3.put("classValue", 5);
        keys.add(map3);

        Collections.sort(keys,
            new Comparator() {
                public int compare(Object left, Object right) {
                    HashMap leftMap = (HashMap) left;
                    HashMap rightMap = (HashMap) right;
                    Integer classValue1 = Integer.parseInt(leftMap.get("classValue").toString());
                    Integer classValue2 = Integer.parseInt(rightMap.get("classValue").toString());
                    int comp = classValue1.compareTo(classValue2);
                    return comp == 0 ? leftMap.get("name").toString().compareTo(rightMap.get("name").toString()) : comp;
                }
            });

        //List the values
        Object[] keyList = keys.toArray();
        for(Integer index = 0; index < keyList.length; index++) {
            System.out.println(keyList[index]);
        }
    }
}

And the output is as following. At first sorts by classValue and then by name.

{name=Ashok Kumar, classValue=5}
{name=Pritom, classValue=5}
{name=Bappi Lahiri, classValue=10}

Grails pagination on a ArrayList

In my recent grails project, i needed to paginate on an array list, so I wrote a function and thought would share it with you all.

---

public List getFilteredList(int max, int offset) {
    max = Math.min(max ?: 25, 100)
    offset = (offset && offset > 0) ?: 0

    List names = getNames() //Loads the complete list
    int total = names.size()
    int upperLimit = findUpperIndex(offset, max, total)
    List filteredNames = names.getAt(offset..upperLimit)
    return filteredNames
}

private static int findUpperIndex(int offset, int max, int total) {
    max = offset + max - 1
    if (max >= total) {
        max -= max - total + 1
    }
    return max
}

So now if offset=20 and max=10, total = 28 so this will generate a list from 21st to 28th elements of the main list.