Two ways of realizing the TreeSet comparator and Comparable__java

TreeSet

Conditions

Same type

Design to sort

Comparable is natural (you can modify the case of a class)

Comparator is custom (in the case of a class cannot be modified) higher priority

Instructions for use:

Generally used is the natural sort, but when the class can not be modified to have to use the comparator method, the following demo using two ways.

Code Overall Description:

The Birthday property of the employee class is the custom class mydate type

Employee by comparable way by default is sorted by name

Then the birth date is sorted using a customized comparator method

Package TestContainer;
	public class MyDate {private int day;
	private int month;

	private int year;
	public int getday () {return day;
	public void Setday (int day) {this.day = day;
	public int getmonth () {return month;
	The public void setmonth (int month) {this.month = month;
	public int getyear () {return year;
		@Override public int hashcode () {final int prime = 31;
		int result = 1;
		result = Prime * result + day;
		result = Prime * result + month;
		result = Prime * result + year;
	return result;
		@Override public boolean equals (Object obj) {if (this = obj) return true;
		if (obj = null) return false;
		if (GetClass ()!= Obj.getclass ()) return false;
		MyDate other = (mydate) obj;
		if (day!= other.day) return false;
		if (month!= other.month) return false;
		if (year!= other.year) return false;
	return true;
	public void setyear (int year) {this.year = year; MyDate (int day, int month, int) {super ();
		This.day = day;
		This.month = month;
	This.year = year;
	Public MyDate () {super ();
	@Override public String toString () {return "mydate [day= + day +", month= "+ month +", year= "+ year +]";
 }

}

Package TestContainer;
Whether to override the CompareTo () and Equals () methods, although the comparison is a string or integer CompareTo () method, it is also necessary to determine whether multiple employee is equal if you put the employee in the TreeSet
	public class Employee implements comparable{private String name;
		@Override public int hashcode () {final int prime = 31;
		int result = 1;
		result = Prime * result + age;
		result = Prime * result + ((birthday = null)? 0:birthday.hashcode ());
		result = Prime * result + ((name = = null) 0:name.hashcode ());
	return result;
		@Override public boolean equals (Object obj) {if (this = obj) return true;
		if (obj = null) return false;
		if (GetClass ()!= Obj.getclass ()) return false;
		Employee other = (employee) obj;
		if (age!= other.age) return false;
		if (birthday = = null) {if (other.birthday!= null) return false;
		else if (!birthday.equals (Other.birthday)) return false;
		if (name = = null) {if (other.name!= null) return false;
		else if (!name.equals (Other.name)) return false;
return true;	private int age;

	Private MyDate birthday;
	Public String GetName () {return name;
	public void SetName (String name) {this.name = name;
	public int getage () {return age;
	public void Setage (int age) {this.age = age;
	Public MyDate Getbirthday () {return birthday;
	public void Setbirthday (mydate birthday) {this.birthday = birthday;
	Public Employee () {super ();
		Public Employee (String name, int age, mydate birthday) {super ();
		THIS.name = name;
		This.age = age;
	This.birthday = Birthday; @Override public String toString () {return "Employee [name=" + name +], age= "+ Age +", birthday= "+ Birthday +
	"]";
			@Override public int compareTo (Object o) {if (o instanceof employee) {Employee employee= (employee) O;
int I=this.getname (). CompareTo (Employee.getname ());
			if (i==0) {//int j=this.getage ()-employee.getage ();////if (j==0) {////////}//return J;//}
		return i;
	return 0; }
}
 

Package TestContainer;

Import static org.junit.assert.*;
Import Java.util.Comparator;

Import Java.util.TreeSet;

Import Org.junit.Test; public class Testemployee {//Natural sort, employee implements comparable interface, and press name to sort @Test public void Test () {Employee E1 = new Em
		Ployee ("Haid", New MyDate (2, 2, 1985));
		Employee E2 = new Employee ("Qiao", New MyDate (13, 10, 1991));
		Employee E3 = new Employee ("Alex", New MyDate (2, 2, 1996));
		Employee E4 = New Employee ("Tom", Panax Notoginseng, New MyDate (2, 2, 1980));

		Employee E5 = new Employee ("Alex", New MyDate (13, 10, 1989)); Custom sort Comparator Comparator Comparator = new Comparator () {public int compare (object O1, Object O2) {if (O1 in
					Stanceof Employee && O2 instanceof Employee} {Employee E1 = (employee) O1;
					Employee E2 = (employee) O2;
					int i = E1.getbirthday (). getyear ()-E2.getbirthday (). getyear ();
						if (i = = 0) {int j = e1.getbirthday (). getmonth ()-E2.getbirthday (). getmonth (); if (j = = 0){return E1.getbirthday (). Getday ()-E2.getbirthday (). Getday ();
					} return J;
				return i;

			return 0;

		}

		};
		TreeSet set = new TreeSet (comparator);
		Set.add (E1);
		Set.add (E2);
		Set.add (E3);
		Set.add (E4);

		Set.add (E5);

	For (object Object:set) System.out.println (object);
 }
}