How to Write Your Own Comparator

package example.comparator;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.Comparator;

import java.util.List;

public class EmpComparator implements Comparator {

    public int compare(Object obj1, Object obj2) {

	Person emp1 = (Person) obj1;

	Person emp2 = (Person) obj2;

	int nameComp = emp1.getFirstName().compareTo(emp2.getFirstName());

	return ((nameComp == 0) ? emp1.getLastName().compareTo(emp2.getLastName()) : nameComp);

    }

    public static void main(String args[]) {

	String names[] = { "Bart", "Hugo", "Lisa", "Marge", "Homer", "Maggie", "Roy" };

	// Convert to list

	List list = new ArrayList(Arrays.asList(names));

	// Ensure list sorted

	Collections.sort(list);

	System.out.println("Sorted list: [length: " + list.size() + "]");

	System.out.println(list);

	// Search for element in list

	int index = Collections.binarySearch(list, "Maggie");

	System.out.println("Found Maggie @ " + index);

	// Search for element not in list

	index = Collections.binarySearch(list, "Jimbo Jones");

	System.out.println("Didn't find Jimbo Jones @ " + index);

	// Insert

	int newIndex = -index - 1;

	list.add(newIndex, "Jimbo Jones");

	System.out.println("With Jimbo Jones added: [length: " + list.size() + "]");

	System.out.println(list);

	// Min should be Bart

	System.out.println(Collections.min(list));

	// Max should be Roy

	System.out.println(Collections.max(list));

	Comparator comp = Collections.reverseOrder();

	// Reversed Min should be Roy

	System.out.println(Collections.min(list, comp));

	// Reversed Max should be Bart

	System.out.println(Collections.max(list, comp));

    }

}

class Person implements Comparable {

    String firstName, lastName;

    public Person(String f, String l) {

	this.firstName = f;

	this.lastName = l;

    }

    public String getFirstName() {

	return firstName;

    }

    public String getLastName() {

	return lastName;

    }

    public String toString() {

	return "[ name=" + firstName + ",name=" + lastName + "]";

    }

    public int compareTo(Object obj) {

	Person emp = (Person) obj;

	int deptComp = firstName.compareTo(emp.getFirstName());

	return ((deptComp == 0) ? lastName.compareTo(emp.getLastName()) : deptComp);

    }

    public boolean equals(Object obj) {

	if (!(obj instanceof Person)) {

	    return false;

	}

	Person emp = (Person) obj;

	return firstName.equals(emp.getFirstName()) && lastName.equals(emp.getLastName());

    }

}