Java 中对日期的操作

Java 中对日期的操作

Java 中对日期的操作 ........................................................................................................ 1

1 日期模板 ...................................................................................................................... 2

2 格式化日期 ................................................................................................................... 2

3 取得当前日期 ............................................................................................................... 3

4 当前时间 ...................................................................................................................... 3

5 1 年前日期 .................................................................................................................... 4

6 明天日期 ...................................................................................................................... 4

7 两个时间之间的天数 ..................................................................................................... 4

8 加半小时 ...................................................................................................................... 4

9 年月周求日期 ............................................................................................................... 5

10 求是星期几................................................................................................................. 5

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11 java 数据类型转换 ........................................................................................................ 5

11.1 如何将字串 String 转换成整数 int....................................................................... 5

11.2 如何将整数 int 转换成字串 String ..................................................................... 5

11.3 例子 .................................................................................................................. 6

11.4 数据类型转换函数 ............................................................................................. 7

12 取得序号加一 ............................................................................................................. 8

1 日期模板

模板定义如下：

y 年号，如 1996

M 月份，如July 或者07

d 月中第几天，如12

H 小时 (24 制 )，如 0、 17

m 分钟,如32

s 钞钟，如55

S 微钞，如978

E 星期几，如Tuesday

D 一年中的第几天，如189

w week in year (Number) 27

W week in month (Number) 2

a am/pm marker (Text) PM

k hour in day (1~24) (Number) 24

K hour in am/pm (0~11) (Number) 0

z time zone (Text) Pacific Standard Time

' escape for text (Delimiter)

'' single quote (Literal) '

2 格式化日期

使用SimpleDateFormat 类格式化日期，如果日期格式不对，会产生异常。

import java.text.* ;

import java.util.* ;

public class TestDate {

public static void main(String[] args) {

String dStr = " 2001.12.12-08.23.21";

Date d = null;

SimpleDateFormat sdf = new SimpleDateFormat(" yyyy.MM.dd- HH.mm.ss");

try {

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d = sdf.parse (dStr);

} catch (ParseException pe) {

System.out.println (pe.getMessage());

}

System.out.println (d);

System.out.println (d.getTime());

}

}

在java.text 包中找到那个SimpleDateFormat 类，给它一个模板，可以parse 成一个Date，然后使用Date

类的getItme() 方法，可以得到一个Long 数据。

3 取得当前日期

public String GetDateTime()

{

Calendar cal = Calendar.getInstance();

SimpleDateFormat formatter = new SimpleDateFormat("yyyy- MM-dd HH:mm:ss");

String mDateTime= formatter.format(cal.getTime());

return (mDateTime);

}

public java.sql.Date GetDate()

{

java.sql.Date mDate;

Calendar cal = Calendar.getInstance();

SimpleDateFormat formatter = new SimpleDateFormat("yyyy- MM-dd HH:mm:ss");

String mDateTime= formatter.format(cal.getTime());

return (java.sql.Date.valueOf (mDateTime));

}

4 当前时间

Calendar cal = Calendar.getInstance();

// SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM- dd HH:mm:ss");

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SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss G E D F w W a E F");

String mDateTime= formatter.format(cal.getTime());

out.println (mDateTime);

out.println ("<br>");

5 1 年前日期

java.util.Date myDate=new java.util.Date();

long myTime=( myDate.getTime()/1000)-60*60*24*365;

myDate.setTime (myTime*1000);

String mDate= formatter.format(myDate);

out.println (mDate);

out.println ("<br>");

6 明天日期

myDate=new java.util.Date();

myTime=(myDate.getTime ()/1000)+60*60*24;

myDate.setTime (myTime*1000);

mDate=formatter.format (myDate);

out.println (mDate);

out.println ("<br>");

7 两个时间之间的天数

SimpleDateFormat myFormatter = new SimpleDateFormat("yyyy-MM- dd");

java.util.Date date= myFormatter.parse("2003-05-1");

java.util.Date mydate= myFormatter.parse("1899-12-30");

long day=( date.getTime()-mydate.getTime())/(24*60*60*1000);

out.println (day);

out.println ("<br>");

8 加半小时

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

java.util.Date date1 = format.parse("2002-02-28 23:16:00");

long Time=( date1.getTime()/1000)+60*30;

date1.setTime (Time*1000);

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String mydate1= formatter.format(date1);

out.println (mydate1);

out.println ("<br>");

9 年月周求日期

SimpleDateFormat formatter2 = new SimpleDateFormat("yyyy-MM F E");

java.util.Date date2= formatter2.parse("2003-05 5 星期五");

SimpleDateFormat formatter3 = new SimpleDateFormat("yyyy-MM-dd");

String mydate2= formatter3.format(date2);

out.println (mydate2);

out.println ("<br>");

10 求是星期几

mydate= myFormatter.parse ("2001-1-1");

SimpleDateFormat formatter4 = new SimpleDateFormat("E");

String mydate3= formatter4.format(mydate);

out.println (mydate3);

out.println ("<br>");

11 java 数据类型转换

11.1 如何将字串 String 转换成整数 int

1). int i = Integer.parseInt([String]); 或

i = Integer.parseInt([String],[int radix]);

2). int i = Integer.valueOf(my_str).intValue();

注: 字串转成Double, Float, Long 的方法大同小异.

11.2 如何将整数 int 转换成字串 String

A. 有叁种方法:

1.) String s = String.valueOf(i);

2.) String s = Integer.toString(i);

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3.) String s = "" + i;

注: Double, Float, Long 转成字串的方法大同小异.

11.3 例子

package cn.com.lwkj.erts.register;

import java.sql.Date;

public class TypeChange {

public TypeChange() {

}

//change the string type to the int type

public static int stringToInt(String intstr)

{

Integer integer;

integer = Integer.valueOf(intstr);

return integer.intValue();

}

//change int type to the string type

public static String intToString(int value)

{

Integer integer = new Integer(value);

return integer.toString();

}

//change the string type to the float type

public static float stringToFloat(String floatstr)

{

Float floatee;

floatee = Float.valueOf(floatstr);

return floatee.floatValue();

}

//change the float type to the string type

public static String floatToString(float value)

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{

Float floatee = new Float(value);

return floatee.toString();

}

//change the string type to the sqlDate type

public static java.sql.Date stringToDate(String dateStr)

{

return java.sql.Date.valueOf(dateStr);

}

//change the sqlDate type to the string type

public static String dateToString(java.sql.Date datee)

{

return datee.toString();

}

public static void main(String[] args)

{

java.sql.Date day ;

day = TypeChange.stringToDate("2003-11-3");

String strday = TypeChange.dateToString(day);

System.out.println(strday);

}

}

11.4 数据类型转换函数

JAVA 中常用数据类型转换函数

虽然都能在JAVA API 中找到，整理一下做个备份。

string->byte

Byte static byte parseByte(String s)

byte->string

Byte static String toString(byte b)

char->string

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Character static String to String (char c)

string->Short

Short static Short parseShort(String s)

Short->String

Short static String toString(Short s)

String->Integer

Integer static int parseInt(String s)

Integer->String

Integer static String tostring(int i)

String->Long

Long static long parseLong(String s)

Long->String

Long static String toString(Long i)

String->Float

Float static float parseFloat(String s)

Float->String

Float static String toString(float f)

String->Double

Double static double parseDouble(String s)

Double->String

Double static String toString(Double)

12 取得序号加一

public int GetMaxID(String vTableName,String vFieldName)

{

int mResult=0;

boolean mConn=true;

String mSql=new String();

mSql = "select max("+vFieldName+")+1 as MaxID from " + vTableName;

try

{

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if (Conn!=null){

mConn=Conn.isClosed ();

}

if (mConn){

OpenConnection();

}

ResultSet result=ExecuteQuery(mSql);

if (result.next ())

{

mResult=result.getInt ("MaxID");

}

result.close ();

if (mConn)

{

CloseConnection();

}

}

catch(Exception e)

{

System.out.println (e.toString());

}

return (mResult);

}

mDocumentId= DbaObj.GetMaxID("Document","DocumentID");