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AscendingCountryCodeComparator.java

import java.util.Comparator;

public class AscendingCountryCodeComparator implements Comparator<String>
{

    /*
     * This method is used to arrange the CountryCodes in Ascending order.
     */
    @Override
    public int compare( String countryCode1, String countryCode2 )
    {

        System.out
                .println("\nCompare method has been called in AscendingCountryCodeComparator,\nto arrange"
                        + " the CountryCodes in ascending order : ");

        System.out.println("countryCode1 = " + countryCode1
                + ", countryCode2 = " + countryCode2 + "\n");

        return countryCode1.compareTo(countryCode2);
    }

}

TreeMapExample.java

import java.util.TreeMap;

/*
 * Example of comparator() method.
 */
public class TreeMapExample
{
    public static void main( String[] args )
    {

        AscendingCountryCodeComparator ascendingCountryCodeComparator = new AscendingCountryCodeComparator();

        TreeMap<String, String> treeMap = new TreeMap<String, String>(
                ascendingCountryCodeComparator);
        /*
         * Key is CountryCode - Value is CountryName
         */

        System.out.println("Key:CN,Value:CHINA is going to be add in treeMap");
        treeMap.put("CN", "CHINA");
    
        System.out.println("Key:BE,Value:BELGIUM is going to be add in treeMap");
        treeMap.put("BE", "BELGIUM");
        
        System.out.println("Key:AF,Value:AFGHANISTAN is going to be add in treeMap");
        treeMap.put("AF", "AFGHANISTAN");
        
        System.out.println("Key:DK,Value:DENMARK is going to be add in treeMap");
        treeMap.put("DK", "DENMARK");

        System.out.println("treeMap : " + treeMap + "\n");

    }
}

Key:CN,Value:CHINA is going to be add in treeMap

Compare method has been called in AscendingCountryCodeComparator,
to arrange the CountryCodes in ascending order : 
countryCode1 = CN, countryCode2 = CN

Key:BE,Value:BELGIUM is going to be add in treeMap

Compare method has been called in AscendingCountryCodeComparator,
to arrange the CountryCodes in ascending order : 
countryCode1 = BE, countryCode2 = CN

Key:AF,Value:AFGHANISTAN is going to be add in treeMap

Compare method has been called in AscendingCountryCodeComparator,
to arrange the CountryCodes in ascending order : 
countryCode1 = AF, countryCode2 = CN


Compare method has been called in AscendingCountryCodeComparator,
to arrange the CountryCodes in ascending order : 
countryCode1 = AF, countryCode2 = BE

Key:DK,Value:DENMARK is going to be add in treeMap

Compare method has been called in AscendingCountryCodeComparator,
to arrange the CountryCodes in ascending order : 
countryCode1 = DK, countryCode2 = BE


Compare method has been called in AscendingCountryCodeComparator,
to arrange the CountryCodes in ascending order : 
countryCode1 = DK, countryCode2 = CN

treeMap : {AF=AFGHANISTAN, BE=BELGIUM, CN=CHINA, DK=DENMARK}