How to calculate 30 days back from today using Calendar in Java

Question

I want to calculate the date 30 days back from today's date.

public void dateSetup(){
        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd ");
        Calendar cal = Calendar.getInstance();
        Calendar calReturn = Calendar.getInstance();
        jDate_timeOfExpectedReturn1.setText(dateFormat.format(cal.getTime()));
        calReturn.add(Calendar.DATE, 30);
        jDate_timeOfLoan1.setText(dateFormat.format(calReturn.getTime()));
    }

Above you can see that I'm extracting today date using Calendar cal = Calendar.getInstance();

How do I calculate the date of 30 days before the extracted date?

Thanks for any help given.

Answer 1

只需使用add()方法-30天

 calReturn.add(Calendar.DATE, -30);

Answer 2

你需要添加-30 ，这将是减法。

calReturn.add(Calendar.DATE, -30);

Answer 3

在add()方法中使用负数作为-30 ，这将像date+(-30) ==> date-30