用java或者c/c++如何将“明天”“一周内” “未来三天“这种词转化为当时的时间呢？这个函数应该如何写，流程思想是什么？请大侠赐教!

public class TestCalendar {    public static void main(String[] args) {        tc.method3("今天");        tc.method3("明天");        tc.method3("未来三天");    }        private void method3(String str){        char c = ' ';        if(str.equals("今天")){            c = 'T';        }else if(str.equals("明天")){            c = 'O';        }else if(str.equals("未来三天")){            c = 'F';        }        Calendar cal = Calendar.getInstance();        int day = cal.get(DATE);        int month = cal.get(MONTH);        switch (c) {        case 'T':            System.out.println(cal.get(MONTH)+"月"+cal.get(DATE)+"日");            break;        case 'O':            cal.add(DATE, 1);            System.out.println(cal.get(MONTH)+"月"+cal.get(DATE)+"日");            break;        case 'F':            System.out.print(cal.get(MONTH)+"月"+cal.get(DATE)+"日到");            cal.add(DATE, 3);            System.out.println(cal.get(MONTH)+"月"+cal.get(DATE)+"日");            break;        default:            break;        }    }}