Java中Date转换为Datetime、String与Date的相互转换

本转换在项目中经常遇见，现简要地说明：

(1) Date转换为Datetime

Datetime在java数据库中对应的是Timestamp，转换如下：

//java.util.Date转换为Timestamp
Date date = new Date();
Timestamp timestamp = new Timestamp(date.getTime()); //2013-01-14 22:45:36.484

(2) String转换为Date

//String转换为java.util.Date
String str = "2013-01-14";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date date = null; //初始化date
try {
    date = sdf.parse(str); //Mon Jan 14 00:00:00 CST 2013
} catch (ParseException e) {
    e.printStackTrace();
}

(3) Date转换为String

//java.util.Date转换为String
Date date = new Date();
DateFormat format = new SimpleDateFormat("yyyy-MM-dd");
String str = format.format(date); //2013-01-14

(4) String转化为java.sql.Date

转换为java.sql.Date目的是要对数据库进行操作

//String转换为java.sql.Date
String str = "2013-01-14";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
java.sql.Date sdate = null; //初始化
try {
    java.util.Date udate = sdf.parse(str);
    sdate = new java.sql.Date(udate.getTime()); //2013-01-14
} catch (ParseException e) {
    e.printStackTrace();
}