JAVA日期计算代码

package client.dao;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Map;

import org.apache.log4j.Logger;

import client.dto.ChargeTermDto;
import client.interfaces.IChargeTerm;

import com.factory.DBConnFactory;

public class ChargeTermDao implements IChargeTerm {
static Logger logger = Logger.getLogger(ChargeTermDao.class.getName());
protected final String SQL_SELECT = "SELECT id ,charge_term FROM "+ getTableName();
protected final String SQL_UPDATE = "UPDATE " + getTableName() + " set charge_term=? ";
public String getRec() {
String result = "0";
Map map = null;
try {
map = DBConnFactory.newInstance().searchToMap(SQL_SELECT);
} catch (Exception e) {
logger.error(e.getMessage());
}
if (map !=null){
result = map.get("charge_term").toString();
}
return result;
}

public boolean update(ChargeTermDto dto) {
boolean result = false;
int i = 0;
try {
i = DBConnFactory.newInstance().update(SQL_UPDATE,
dto.getChargeTerm());
if (i > 0)
result = true;

} catch (Exception ex) {
logger.error(ex.getMessage());
}

return result;
}

public String getTableName() {
return "charge_term";
}

public String getChargeTerm(String feeMonth) {
StringBuffer str = new StringBuffer(feeMonth);
int year = Integer.parseInt(str.substring(0, 4));
int month = Integer.parseInt(str.substring(4, 6));
int day = Integer.parseInt(this.getRec());

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Calendar calendar = Calendar.getInstance();
calendar.set(year, month, day);
String result = sdf.format(calendar.getTime());
return result;
}
}