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Employee.java
EmployeeNameComparator.java
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Employee.java
public class Employee { private int employeeId; private String name; public Employee( int employeeId, String name ) { super(); this.employeeId = employeeId; this.name = name; } public int getEmployeeId() { return employeeId; } public void setEmployeeId( int employeeId ) { this.employeeId = employeeId; } public String getName() { return name; } public void setName( String name ) { this.name = name; } @Override public String toString() { return "Employee [employeeId=" + employeeId + ", name=" + name + "]"; } }
import java.util.Comparator; public class EmployeeNameComparator implements Comparator<Employee> { /* * This method is used to arrange the employee objects in Descending order based * on employee name. */ @Override public int compare( Employee employee1, Employee employee2 ) { System.out .println("\nCompare method has been called in EmployeeNameComparator,\nto arrange the" + " employee objects in Descending order based on employee name : "); System.out.println("employee1 = " + employee1 + ", employee2 = " + employee2 + "\n"); return employee2.getName().compareTo(employee1.getName()); } }
import java.util.TreeSet; /* * Example of TreeSet(Comparator<? super E> comparator) Constructor. */ public class TreeSetExample { public static void main(String[] args) { EmployeeNameComparator employeeNameComparator = new EmployeeNameComparator(); /* * Constructs a new, empty tree set, sorted according to the specified * comparator. * * All elements inserted into the set must be mutually comparable by the * specified comparator: comparator.compare(e1, e2) must not throw a * ClassCastException for any elements e1 and e2 in the set. * * If the user attempts to add an element to the set that violates this * constraint, the add call will throw a ClassCastException. */ TreeSet<Employee> treeSet = new TreeSet<Employee>( employeeNameComparator); Employee carol = new Employee(3, "Carol"); Employee balu = new Employee(5, "Balu"); Employee ajay = new Employee(4, "Ajay"); Employee dave = new Employee(1, "Dave"); System.out.println(carol + " is going to be add in treeSet"); treeSet.add(carol); System.out.println(balu + " is going to be add in treeSet"); treeSet.add(balu); System.out.println(ajay + " is going to be add in treeSet"); treeSet.add(ajay); System.out.println(dave + " is going to be add in treeSet"); treeSet.add(dave); System.out.println("treeSet : " + treeSet + "\n"); for (Employee employee : treeSet) { System.out.println("Name : " + employee.getName()); System.out.println("Employee ID : " + employee.getEmployeeId()); System.out.println("-----------------------------------"); } } }
Employee [employeeId=3, name=Carol] is going to be add in treeSet Compare method has been called in EmployeeNameComparator, to arrange the employee objects in Descending order based on employee name : employee1 = Employee [employeeId=3, name=Carol], employee2 = Employee [employeeId=3, name=Carol] Employee [employeeId=5, name=Balu] is going to be add in treeSet Compare method has been called in EmployeeNameComparator, to arrange the employee objects in Descending order based on employee name : employee1 = Employee [employeeId=5, name=Balu], employee2 = Employee [employeeId=3, name=Carol] Employee [employeeId=4, name=Ajay] is going to be add in treeSet Compare method has been called in EmployeeNameComparator, to arrange the employee objects in Descending order based on employee name : employee1 = Employee [employeeId=4, name=Ajay], employee2 = Employee [employeeId=3, name=Carol] Compare method has been called in EmployeeNameComparator, to arrange the employee objects in Descending order based on employee name : employee1 = Employee [employeeId=4, name=Ajay], employee2 = Employee [employeeId=5, name=Balu] Employee [employeeId=1, name=Dave] is going to be add in treeSet Compare method has been called in EmployeeNameComparator, to arrange the employee objects in Descending order based on employee name : employee1 = Employee [employeeId=1, name=Dave], employee2 = Employee [employeeId=5, name=Balu] Compare method has been called in EmployeeNameComparator, to arrange the employee objects in Descending order based on employee name : employee1 = Employee [employeeId=1, name=Dave], employee2 = Employee [employeeId=3, name=Carol] treeSet : [Employee [employeeId=1, name=Dave], Employee [employeeId=3, name=Carol], Employee [employeeId=5, name=Balu], Employee [employeeId=4, name=Ajay]] Name : Dave Employee ID : 1 ----------------------------------- Name : Carol Employee ID : 3 ----------------------------------- Name : Balu Employee ID : 5 ----------------------------------- Name : Ajay Employee ID : 4 -----------------------------------
https://sites.google.com/site/javaee4321/java-collections/TreeSetDemoEmployeesAscComparatorDescName.zip?attredirects=0&d=1
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