java中Calendar.getInstance()和new Date()的差别是什么?

java中CalendargetInstance()和new Date()的差别如下：

CalendargetInstance()是获取一个Calendar对象并可以进行时间的计算，时区的指定

new Date()是创建了一个date对象，默认是utc格式的。

二者可以相互转化：

Calendar calendar = CalendargetInstance();

// 从一个 Calendar 对象中获取 Date 对象

Date date = calendargetTime();

// 将 Date 对象反应到一个 Calendar 对象中，

// Calendar/GregorianCalendar 没有构造函数可以接受 Date 对象

// 所以我们必需先获得一个实例，然后设置 Date 对象

calendarsetTime(date);

万年历代码：

/

@(#)AidyCalenderjava

@author

@version 100 2008/7/19

/

import javaawt;

import javaawtevent;

import javalangStringBuffer;

import javaxswing;

import javautil;

import javaxswingTimer;

import javaxswingborder;

public class AidyCalender extends JFrame implements ActionListener,ItemListener{

Date date = new Date();

private GregorianCalendar gregorianCalendar = new GregorianCalendar();

//定义中英文字符数组存储星期信息,用于转换显示

private String[] stringWeekEn = new String[] { "SUN", "MON", "TUE", "WED",

"THU", "FRI", "SAT" };

private String[] stringWeekCn = new String[] { "星期日", "星期一", "星期二", "星期三",

"星期四", "星期五", "星期六" };

//定义存储月份的信息数组,用于转换显示方示

private String[] stringMonthEn = new String[] { "Jan", "Feb", "Mar", "Apr",

"May", "Jun", "Jul", "Aug", "Sept", "Oct", "Nov", "Dec" };

private String[] stringMonthCn = {"一月","二月","三月","四月","五月","六月",

"七月","八月","九月","十月","十一月","十二月"};

private String[] sysNowTime = new String[6];//sysNowTime 用于存储系统时间的变量

private String[] sysRunTime = new String[6];

private JLabel []labelWeek = new JLabel[7];

private JLabel []labelDay = new JLabel[42];

private JLabel labelTime = new JLabel();

private JPanel panel1 = new JPanel();

private JPanel panel2 = new JPanel();

private JPanel panel3 = new JPanel();

private JComboBox combo1 = new JComboBox();

private JComboBox combo2 = new JComboBox();

private JButton buttonToday = new JButton();

private Border border = BorderFactorycreateRaisedBevelBorder();

private Border border1 = BorderFactorycreateLineBorder(Colorcyan,3);

public AidyCalender(String title) {

super(title);

for (int y = 1900; y < 2101; y++) {

combo1addItem(" " + new Integer(y)toString()+"年");

}

for (int m = 0;m<12;m++){

combo2addItem(" "+stringMonthCn[m]);

}

buttonTodaysetText("今 天");

setLayout(new FlowLayout());

add(panel1);

add(panel2);

add(panel3);

panel1setLayout(new GridLayout(1,3,10,0));

panel1add(combo1);

combo1addItemListener(this);

panel1add(combo2);

combo2addItemListener(this);

panel1add(buttonToday);

buttonTodayaddActionListener(this);

labelTimesetFont(new Font("宋体",FontPLAIN,16));

labelTimesetForeground(ColorMAGENTA);

panel1add(labelTime);

Timer time = new Timer(1000,new TimerListener());

timeaddActionListener(new TimerListener());

//timesetRepeats(true);

timestart();

//labelTimeaddAncestorListener(new TimerListener());

panel2setLayout(new GridLayout(7,7,0,10));

panel2setBackground(Colorwhite);

for(int i=0;i<7;i++){

labelWeek[i] = new JLabel();

labelWeek[i]setHorizontalAlignment(0);

if(i==0||i==6){

labelWeek[i]setBackground(Colorblue);

labelWeek[i]setForeground(ColorRED);

labelWeek[i]setFont(new Font("黑体",FontBOLD,14));

}

else{

labelWeek[i]setForeground(ColorBLACK);

labelWeek[i]setFont(new Font("新宋体",FontPLAIN,14));

}

labelWeek[i]setText(stringWeekCn[i]);

panel2add(labelWeek[i]);

}

for(int i= 0;i<42;i++){

labelDay[i] = new JLabel();

labelDay[i]setHorizontalAlignment(0);

labelDay[i]setText("");

panel2add(labelDay[i]);

}

addWindowListener(new WindowAdapter(){

public void windowClosing(WindowEvent e){

Systemexit(0);

}

});

setSize(300,300);

setBounds(250, 200, 400, 360);

setVisible(true);

setResizable(false);

setDefaultCloseOperation(JFrameEXIT_ON_CLOSE);

getSysDate();

setNowDate();

}

public void actionPerformed(ActionEvent ae){

if(aegetSource()==buttonToday){

setNowDate();

}

}

public void itemStateChanged(ItemEvent aa){

setChangeDate();

}

public int turnWeek(String week){

int i;

for(i=0;i<7;i++)

if(weekequalsIgnoreCase(stringWeekEn[i]))

break;

return i;

}

public int turnMonth(String month){

/

int turnMonth(String month)

@month 系统日期中的月,诸如Jan\Feb

@return int

返回一个整数值,用于寻找stringMonthCn[]数组中对应的中文月份

/

int i;

for(i=0;i<12;i++)

if(monthequalsIgnoreCase(stringMonthEn[i]))

break;

return i;

}

/

setNowDate()

设置当前系统日期

/

public void setNowDate(){

setSysDate(getNowYear(),getNowMonth());

getSysRunDate();

setDateNull();

combo1setSelectedIndex(getShowYear() - 1900);

combo2setSelectedIndex(getShowMonth());

setDays(getMonthDays(getNowYear(),getNowMonth()),getInitWeek(sysRunTime[0]),getNowDay());

//labelTimesetText(sysNowTime[3]);

//labelTimesetHorizontalAlignment(0);

}

/Integer getShowYear()

获取组合框中应该显示的年份

/

public void setSysDate(int year,int month){

gregorianCalendarset(year,month,1);

}

public void setDateNull(){

for(int i=0;i<42;i++){

labelDay[i]setText("");

}

}

public void setChangeDate(){

setSysDate(getComboYear(),getComboMonth());

getSysRunDate();

setDateNull();

setDays(getMonthDays(getComboYear(),getComboMonth()),getInitWeek(sysRunTime[0]),-1);

}

public int getMonthDays(int year, int month) {

/

返回所选年月的天数,因为数组中的数值从0开始,所以3\5\8\10分别代表4\6\9\11几个小月

而1代表2月,经过是否为闰年判断,选择返回28或29天

其余月份为大月,返回31天

/

switch (month) {

case 3:

case 5:

case 8:

case 10:

return 30;//小月返回30天

case 1:

if (gregorianCalendarisLeapYear(year)) {

//isLeapYear(year)确定当前纪元中的指定年份是否为闰年。

return 29;

} else {

return 28;

}//闰年的二月返回29天，平年返回28天

default:

return 31;

//大月返回31天

}

}

/

int getComboYear()

获取组合框中的年份

/

public void getSysDate(){

date = gregorianCalendargetTime();

sysNowTime = (datetoString())split(" ");

}

public void getSysRunDate(){

date = gregorianCalendargetTime();

sysRunTime = (datetoString())split(" ");

}

public int getComboYear(){

return combo1getSelectedIndex()+1900;

}

/

int getComboMonth()

获取月组合框中的整数值,

/

public int getComboMonth(){

return combo2getSelectedIndex();

}

public int getInitWeek(String initWeek){

/

getWeekNow(String initWeek)

@para nowWeek 系统日期中的星期

返回当月中的1号是从星期几开始

/

int nowWeek = 0 ;

for(int i = 0;i<7;i++){

if(initWeekequalsIgnoreCase(stringWeekEn[i])){

nowWeek = i;

break;

}

}

return nowWeek;

}

public int getNowYear(){

return IntegerparseInt(sysNowTime[5]);

}

public int getNowMonth(){

int nowMonth=0;

for(int i=0;i<12;i++){

if(sysNowTime[1]equalsIgnoreCase(stringMonthEn[i]));

nowMonth=i;

break;

}

return nowMonth;

}

public int getNowDay(){

return IntegerparseInt(sysNowTime[2]);

}

public Integer getShowYear(){

return IntegerparseInt(sysNowTime[5]);

}

public Integer getShowMonth(){

/

Integer getShowMonth()

获取在组给框中显示的中文格式月份:如七月\八月等

/

return turnMonth(sysNowTime[1]);

}

public void setDays(int monthDays,int initWeek,int day){

/

void setDays(int monthDays,int initWeek,int day)

@para monthDays 本月天数

@para initWeek 初始星期

@para day 今天日

设置月历

/

setDateNull();

for(int i=initWeek;i<initWeek+monthDays+1;i++){

if((i-initWeek+1)==day){

labelDay[i]setBorder(border1);

labelDay[i]setForeground(ColorBLUE);

labelDay[i]setFont(new Font("黑体",FontBOLD,20));

}else if((i%7==0)||(i%7==6))

labelDay[i]setForeground(ColorRED);

else{

labelDay[i]setForeground(ColorBLACK);

}

labelDay[i]setText(StringvalueOf(i-initWeek+1));

}

for(int i=initWeek+monthDays;i<42;i++)

labelDay[i]setText("");

}

class TimerListener implements ActionListener{

//AdapterDemo var=new AdapterDemo("万年历程序--Aidy");

public void actionPerformed(ActionEvent e) {

GregorianCalendar g = new GregorianCalendar();

String clock = new String((ggetTime()toString()split(" "))[3]);

labelTimesetText(clock);

}

}

public static void main(String args[])

{

try{

UIManagersetLookAndFeel(UIManagergetSystemLookAndFeelClassName());

}catch(Exception e){

throw new RuntimeException(e);

}

AidyCalender var=new AidyCalender("万年历程序--Aidy");

}

}

记事本代码这里已经贴不上了。你百度HI我，我给你。

Date类型并没有格式，只有转换成String格式的时候让格式化显示。

new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")format(new Date());

Calendar calendar = CalendargetInstance();

int year = IntegerparseInt(datetimesubstring(0,4));

int month = IntegerparseInt(datetimesubstring(5,7));

int date = IntegerparseInt(datetimesubstring(8,10));

int hour = IntegerparseInt(datetimesubstring(11,13));

int minute = IntegerparseInt(datetimesubstring(14,16));

//int second = IntegerparseInt(datetimesubstring(17,19));

if(calendarget(CalendarYEAR)>year){

int y = calendarget(CalendarYEAR)-year;

扩展资料：

Date类可以在javautil包中找到，用一个long类型的值表示一个指定的时刻。它的一个有用的构造函数是Date()，创建一个表示创建时刻的对象。getTime()方法返回Date对象的long值。

import javautil;

public class Now {

public static void main(String[] args) {

Date now = new Date();

long nowLong = nowgetTime();

Systemoutprintln("Value is " + nowLong);

-java日期函数

分类: 电脑/网络 >> 程序设计 >> 其他编程语言

问题描述:

我想计算2个算法程序运行的时间，做一下比较

JAVA中有那些计算时间函数？最好以毫秒显示出来。

我知道SystemcurrentTimeMillis()

但是不知道为什么，几个程序运行的时间都一样，都是16ms，也不知道是我程序太小了

还是写的不对，大家还知道别的计算时间的函数没？最好在程序开始计算，到程序最后

结束，最后显示一下时间。

解析:

import javautil;

public class RunningTime

{

public static void main(String argc[]) throws InterruptedException

{

int i=0,j=0;

long k=0,begin,end,time;

Date mydate=new Date();

begin=mydategetTime();

for (;i<100;i++)

{

for(;j<100;j++)

{

ThreadcurrentThread()sleep(5);

k+=ij;

}

}

Date mydate2=new Date();

end=mydate2getTime();

time=end-begin;

Systemoutprintln(begin+"运行时间为："+time+" "+end);

}

}

计算运算时间的程序

应该这样写

Calendar nowTime = CalendargetInstance();

Date nowDate = (Date) nowTimegetTime();

Calendar afterTime = CalendargetInstance();

afterTimeadd(CalendarMONTH, 5);

Date afterDate = (Date) afterTimegetTime();

我想说得是 java已经不推荐使用date类了，所以尽量用Calendar 来实现

public class DateCalcu {

public static String getYesterday(String Today) {

String Yes = "";

String year = "", month = "", day = "";

int y = 0, m = 0, d = 0;

year = Todaysubstring(0, 4);

month = Todaysubstring(4, 6);

day = Todaysubstring(6, 8);

y = IntegerparseInt(year);

m = IntegerparseInt(month);

d = IntegerparseInt(day);

d = d - 1;

if (d == 0) {

m = m - 1;

if (m == 1 || m == 3 || m == 5 || m == 7 || m == 8 || m == 10) {

d = 31;

}

if (m == 2)

if ((y % 4 == 0 && y % 100 != 0) || (y % 400 == 0)) // 如果是闰年

d = 29;

else

d = 28;

else if (m != 0)

d = 30;

}

if (m == 0) {

y = y - 1;

m = 12;

d = 31;

}

year = StringvalueOf(y);

if (m < 10)

month = "0" + StringvalueOf(m);

else

month = StringvalueOf(m);

if (d < 10)

day = "0" + StringvalueOf(d);

else

day = StringvalueOf(d);

Yes = year + month + day;

return Yes;

}

public static void main(String args[]) {

String yesterday = "20090301";

Systemoutprintln("今天是" + yesterday);

yesterday = getYesterday(yesterday);

Systemoutprintln("昨天是" + yesterday);

}

}

////////

//看看符合不符合你的要求