Let's understand this by example
import java.util.Date;
import java.util.Date;
public class Refree {
public static void main(String args[]) {
Date date = new Date();
Dater coach = new Dater(date);
System.out.println(coach.date);
date.setYear(1111);
System.out.println(coach.date);
}
}
class Dater {
public Date date;
Dater(Date date) {
this.date = date;
}
}
This program will print
Mon Dec 02 16:33:48 IST 2013
Mon Dec 02 16:33:48 IST 3011
But in line date.setYear(1111); we only want to change the value of date and not coach instance But this code is changing values of date as well as coach.
So how can we avoid that :
Let's see another version of same program
import java.util.Date;
public class Refree {
public static void main(String args[]) {
Date date = new Date();
Dater coach = new Dater(date);
System.out.println(coach.date);
date.setYear(1111);
System.out.println(coach.date);
}
}
class Dater {
public Date date;
Dater(Date date) {
this.date = new Date(date.getTime());
}
}
import java.util.Date;
import java.util.Date;
public class Refree {
public static void main(String args[]) {
Date date = new Date();
Dater coach = new Dater(date);
System.out.println(coach.date);
date.setYear(1111);
System.out.println(coach.date);
}
}
class Dater {
public Date date;
Dater(Date date) {
this.date = date;
}
}
This program will print
Mon Dec 02 16:33:48 IST 2013
Mon Dec 02 16:33:48 IST 3011
But in line date.setYear(1111); we only want to change the value of date and not coach instance But this code is changing values of date as well as coach.
So how can we avoid that :
Let's see another version of same program
import java.util.Date;
public class Refree {
public static void main(String args[]) {
Date date = new Date();
Dater coach = new Dater(date);
System.out.println(coach.date);
date.setYear(1111);
System.out.println(coach.date);
}
}
class Dater {
public Date date;
Dater(Date date) {
this.date = new Date(date.getTime());
}
}
This program will print
Mon Dec 02 16:36:36 IST 2013
Mon Dec 02 16:36:36 IST 2013
So that's what we wanted..