try{
    Date.valueOf(String aString);
}
catch(Exception ex){
    System.err.println("The format of string is not correct");
}

或者

public class forother {
    public static void main(String[] args){
       
        SimpleDateFormat s=new SimpleDateFormat("yyyy-MM-dd' 'HH:mm:ss");
      
        String ooo="2005-02-18 15:39:15";
        String ppp="2005-02-01 15:25:15";     
        try{
        Date tt=s.parse(ooo);
        Date yy=s.parse(ppp);
        long aa;
        if(tt.getTime()>yy.getTime())
            aa=tt.getTime()-yy.getTime();
        else
            aa=yy.getTime()-tt.getTime();
        long date=aa/1000/60/60/24;
        System.out.println("***");
        System.out.println("hahahha"+date);
        System.out.println("*******");
        }catch(Exception e){
           
        }
      
    }
}