Java, how to add and subtract operations on date

Today in doing the project, met the requirements for addition and subtraction of time to operate, according to the date string passed in the operating parameters ( "+", "-"), addend (the number of days to be operated), of date addition and subtraction operations, the query data, wrote a Demo class test, debug normal by subtraction, now share the code below, I hope to help friends encountered!

 

Package com.ltw.test; 
 
Import the java.text.SimpleDateFormat;
 Import java.util.Date;
 Import a java.util.GregorianCalendar; 
 
public  class the Test { 
 
    @SuppressWarnings ( "deprecation" )
     public  static  void main (String [] args) { 
        
        // the passed date string, the operating parameters ( "+", "-"), addend (days to be operated), the operation of subtraction date 
        string dateStr = "2020-03-26 18:20: "23 ; 
        
        // (- being given a string is Date.parse (), alternatively may be implemented through such discovery belt '') into the format of the original time 
        string str = dateStr.replace (" - " ," / " ); 
        
        // add and subtract time type 
        String operator ="+";
        
        //Plus or minus the number of days 
        Integer = 20 is I ; 
        
        // custom variable reception time conversion value 
        Long J = 0 ; 
        a Date DATE = null ; 
        
        the try { 
            J = Date.parse (STR); 
            DATE = new new a Date (J); 
        } the catch ( E Exception) { 
            e.printStackTrace (); 
        } 
        the GregorianCalendar GC = new new the GregorianCalendar (); 
        gc.setTime (DATE); 
 
        IF ( "+" .equals (operator)) { 
            gc.add (GregorianCalendar.DATE, I);
 
        } else if ("-".equals(operator)) {
            gc.add(GregorianCalendar.DATE, (-i));
        }
        
        Date a = gc.getTime();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        
        System.out.println(sdf.format(a));
        
    }
}

 

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