public class Person implements Comparable<Person> {

private String name;

public Person(String name) {

setName(name);

}

public void setName(String name) {

if (name == null || name.equals("")) {

throw new IllegalArgumentException("name can't be null or empty");

}

this.name = name;

}

public String getName() {

return name;

}

public String toString() {

return name;

}

public int compareTo(Person other) {

return name.compareTo(other.name);

}

public boolean equals(Object other) {

if (null == other) return false;

if (this == other) return true;

if (!(other instanceof Person)) return false;

Person that = (Person) other;

return this.name.equals(that.name);

}

public int hashCode() {

return name.charAt(0) - 'A';

}

}