使用equals比较Java中的日期

Question

* UPDATE *I have an instance in my class java.util.Date shippingDate which I need to compare whether it is equal to current date or not.

java.util.Date shippingDate ;
Calendar g = new GregorianCalendar();
shippingDate=g.getTime();
if(shippingDate.equals(new Date()))
{
System.out.println("Match found");
}

Equals is overridden in Date, so it should execute the sysout.But its not printing anything.

PS#I am not allowed to use Joda Time library.

UPDATE- Is there any other way to compare shippingDate with current Date. I don't want to hardcode the current date using SimpleDateFormat . It has to be generated from system.

Answer 1

The Javadoc gives a clue (emphasis mine):

public Date()

Allocates a Date object and initializes it so that it represents the time at which it was allocated, measured to the nearest millisecond .

Answer 2

When you create a new Date object, it takes the current time of the system, so both dates actually differ in the milliseconds passed between lines

Calendar g = new GregorianCalendar();

and

if(shippingDate.equals(new Date()))

Answer 3

have you noticed that you have two lines and at line 1 you get calendar object and you compare the same with date object at line 2 , understand that there is millisecond difference between execution time of both two so it would never be same.

java.util.Date shippingDate ;
Calendar g = new GregorianCalendar(); //line 1
shippingDate=g.getTime();
if(shippingDate.equals(new Date())) //line 2
{
System.out.println("Match found");
}

The result would never be equal if you try to compare two different objects created in multiple statements.

---

Addressing to your question in update : get time in milliseconds using shippingDate.getTime() and then to compare this with system time use System.currentTimeMillis() or you can also use System.nanoTime() but the result would never be same