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copied!<p>Here a complete example :</p> <p>Suppose we have a Person class like :</p> <pre><code>public class Person { protected String fname; protected String lname; public Person() { } public Person(String fname, String lname) { this.fname = fname; this.lname = lname; } public boolean equals(Object objet) { if(objet instanceof Person) { Person p = (Person) objet; return (p.getFname().equals(this.fname)) && p.getLname().equals(this.lname)); } else return super.equals(objet); } @Override public String toString() { return "Person(fname : " + getFname + ", lname : " + getLname + ")"; } /** Getters and Setters **/ } </code></pre> <p>Now we create a comparator : </p> <pre><code>import java.util.Comparator; public class ComparePerson implements Comparator<Person> { @Override public int compare(Person p1, Person p2) { if(p1.getFname().equalsIgnoreCase(p2.getFname())) { return p1.getLname().compareTo(p2.getLname()); } return p1.getFname().compareTo(p2.getFname()); } } </code></pre> <p>Finally suppose we have a group of persons : </p> <pre><code>import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; import java.util.List; public class Group { protected List<Person> listPersons; public Group() { this.listPersons = new ArrayList<Person>(); } public Group(List<Person> listPersons) { this.listPersons = listPersons; } public void order(boolean asc) { Comparator<Person> comp = asc ? new ComparePerson() : Collections.reverseOrder(new ComparePerson()); Collections.sort(this.listPersons, comp); } public void display() { for(Person p : this.listPersons) { System.out.println(p); } } /** Getters and Setters **/ } </code></pre> <p>Now we try this :</p> <pre><code>import java.util.ArrayList; import java.util.List; public class App { public static void main(String[] args) { Group g = new Group(); List listPersons = new ArrayList<Person>(); g.setListPersons(listPersons); Person p; p = new Person("A", "B"); listPersons.add(p); p = new Person("C", "D"); listPersons.add(p); /** you can add Person as many as you want **/ g.display(); g.order(true); g.display(); g.order(false); g.display(); } } </code></pre>

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