Mega Code Archive
Writing Your own Comparator
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import java.util.Arrays;
import java.util.Comparator;
import java.util.Set;
import java.util.TreeSet;
class Employee implements Comparable {
String department, name;
public Employee(String department, String name) {
this.department = department;
this.name = name;
}
public String getDepartment() {
return department;
}
public String getName() {
return name;
}
public String toString() {
return "[dept=" + department + ",name=" + name + "]";
}
public int compareTo(Object obj) {
Employee emp = (Employee) obj;
int deptComp = department.compareTo(emp.getDepartment());
return ((deptComp == 0) ? name.compareTo(emp.getName()) : deptComp);
}
public boolean equals(Object obj) {
if (!(obj instanceof Employee)) {
return false;
}
Employee emp = (Employee) obj;
return department.equals(emp.getDepartment()) && name.equals(emp.getName());
}
public int hashCode() {
return 31 * department.hashCode() + name.hashCode();
}
}
class EmpComparator implements Comparator {
public int compare(Object obj1, Object obj2) {
Employee emp1 = (Employee)obj1;
Employee emp2 = (Employee)obj2;
int nameComp = emp1.getName().compareTo(emp2.getName());
return ((nameComp == 0) ?
emp1.getDepartment().compareTo(emp2.getDepartment()) :
nameComp);
}
}
public class MainClass {
public static void main(String args[]) {
Employee emps[] = {
new Employee("Finance", "A"),
new Employee("Finance", "B"),
new Employee("Finance", "C"),
new Employee("Engineering", "D"),
new Employee("Engineering", "E"),
new Employee("Engineering", "F"),
new Employee("Sales", "G"),
new Employee("Sales", "H"),
new Employee("Support", "I"), };
Set set = new TreeSet(new EmpComparator());
set.addAll(Arrays.asList(emps));
System.out.println(set);
}
}
[[dept=Finance,name=A], [dept=Finance,name=B], [dept=Finance,name=C], [dept=Engineering,name=D], [dept=Engineering,name=E], [dept=Engineering,name=F], [dept=Sales,name=G], [dept=Sales,name=H], [dept=Support,name=I]]
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