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1、计算某一月份的最大天数
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Calendar time=Calendar.getInstance();
time.clear();
time.set(Calendar.YEAR,year);
time.set(Calendar.MONTH,i-1);//注意,Calendar对象默认一月为0
intday=time.getActualMaximum(Calendar.DAY_OF_MONTH);//本月份的天数
注：在使用set方法之前，必须先clear一下，否则很多信息会继承自系统当前时间。
2、Calendar和Date的转化
(1) Calendar转化为Date
Calendar cal=Calendar.getInstance();
Date date=cal.getTime();
(2) Date转化为Calendar
Date date=new Date();
Calendar cal=Calendar.getInstance();
cal.setTime(date);
3、格式化输出日期时间
Date date=new Date();
SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
System.out.println(df.format(date));
4、计算一年中的第几星期
(1)计算某一天是一年中的第几星期
Calendar cal=Calendar.getInstance();
cal.set(Calendar.YEAR, 2006);
cal.set(Calendar.MONTH, 8);
cal.set(Calendar.DAY_OF_MONTH, 3);
int weekno=cal.get(Calendar.WEEK_OF_YEAR);
(2)计算一年中的第几星期是几号
SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");
Calendar cal=Calendar.getInstance();
cal.set(Calendar.YEAR, 2006);
cal.set(Calendar.WEEK_OF_YEAR, 1);
cal.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
System.out.println(df.format(cal.getTime()));
以下是两个类，请楼主分别存成两个java文件:
其中
MainFrame.java是显示日历程序，Clock.java是日历计算程序。编译后运行MainFrame这个类即可。
1.MainFrame.java
---
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Date;
import java.util.Calendar;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class MainFrame extends JFrame {
/** *//**
*
*/
private static final long serialVersionUID = 1L;
JPanel panel = new JPanel(new BorderLayout());
JPanel panel1 = new JPanel();
JPanel panel2 = new JPanel(new GridLayout(7, 7));
JPanel panel3 = new JPanel();
JLabel[] label = new JLabel[49];
JLabel y_label = new JLabel("年份");
JLabel m_label = new JLabel("月份");
JComboBox com1 = new JComboBox();
JComboBox com2 = new JComboBox();
int re_year, re_month;
int x_size, y_size;
String year_num;
Calendar now = Calendar.getInstance(); // 实例化Calendar
MainFrame() {
super("万年历");
setSize(300, 350);
x_size = (int) (Toolkit.getDefaultToolkit().getScreenSize().getWidth());
y_size = (int) (Toolkit.getDefaultToolkit().getScreenSize().getHeight());
setLocation((x_size - 300) / 2, (y_size - 350) / 2);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
panel1.add(y_label);
panel1.add(com1);
panel1.add(m_label);
panel1.add(com2);
for (int i = 0; i 49; i++) {
label[i] = new JLabel("", JLabel.CENTER);// 将显示的字符设置为居中
panel2.add(label[i]);
}
panel3.add(new Clock(this));
panel.add(panel1, BorderLayout.NORTH);
panel.add(panel2, BorderLayout.CENTER);
panel.add(panel3, BorderLayout.SOUTH);
panel.setBackground(Color.white);
panel1.setBackground(Color.white);
panel2.setBackground(Color.white);
panel3.setBackground(Color.white);
Init();
com1.addActionListener(new ClockAction());
com2.addActionListener(new ClockAction());
setContentPane(panel);
setVisible(true);
setResizable(false);
}
class ClockAction implements ActionListener {
public void actionPerformed(ActionEvent arg0) {
int c_year, c_month, c_week;
c_year = Integer.parseInt(com1.getSelectedItem().toString()); // 得到当前所选年份
c_month = Integer.parseInt(com2.getSelectedItem().toString()) - 1; // 得到当前月份，并减1,计算机中的月为0－11
c_week = use(c_year, c_month); // 调用函数use，得到星期几
Resetday(c_week, c_year, c_month); // 调用函数Resetday
}
}
public void Init() {
int year, month_num, first_day_num;
String log[] = { "日", "一", "二", "三", "四", "五", "六" };
for (int i = 0; i 7; i++) {
label[i].setText(log[i]);
}
for (int i = 0; i 49; i = i + 7) {
label[i].setForeground(Color.red); // 将星期日的日期设置为红色
}
for (int i = 6; i 49; i = i + 7) {
label[i].setForeground(Color.green);// 将星期六的日期设置为绿色
}
for (int i = 1; i 10000; i++) {
com1.addItem("" + i);
}
for (int i = 1; i 13; i++) {
com2.addItem("" + i);
}
month_num = (int) (now.get(Calendar.MONTH)); // 得到当前时间的月份
year = (int) (now.get(Calendar.YEAR)); // 得到当前时间的年份
com1.setSelectedIndex(year - 1); // 设置下拉列表显示为当前年
com2.setSelectedIndex(month_num); // 设置下拉列表显示为当前月
first_day_num = use(year, month_num);
Resetday(first_day_num, year, month_num);
}
public int use(int reyear, int remonth) {
int week_num;
now.set(reyear, remonth, 1); // 设置时间为所要查询的年月的第一天
week_num = (int) (now.get(Calendar.DAY_OF_WEEK));// 得到第一天的星期
return week_num;
}
@SuppressWarnings("deprecation")
public void Resetday(int week_log, int year_log, int month_log) {
int month_day_score; // 存储月份的天数
int count;
month_day_score = 0;
count = 1;
Date date = new Date(year_log, month_log + 1, 1); // now
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.MONTH, -1); // 前个月
month_day_score = cal.getActualMaximum(Calendar.DAY_OF_MONTH);// 最后一天
for (int i = 7; i 49; i++) { // 初始化标签
label[i].setText("");
}
week_log = week_log + 6; // 将星期数加6，使显示正确
month_day_score = month_day_score + week_log;
for (int i = week_log; i month_day_score; i++, count++) {
label[i].setText(count + "");
}
}
public static void main(String[] args) {
JFrame.setDefaultLookAndFeelDecorated(true);
new MainFrame();
}
}
2.Clock.java
-----
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Date;
import java.util.Calendar;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
//显示时间的类：Clock
/** *//**
* Clock.java
* Summary 数字时间显示
* Created on
* @author
* remark
*/
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.text.SimpleDateFormat;
import java.util.Calendar;
class Clock extends Canvas implements Runnable{
/** *//**
*
*/
private static final long serialVersionUID = 3660124045489727166L;
MainFrame mf;
Thread t;
String time;
public Clock(MainFrame mf){
this.mf=mf;
setSize(280,40);
setBackground(Color.white);
t=new Thread(this); //实例化线程
t.start(); //调用线程
}
public void run(){
while(true){
try{
Thread.sleep(1000); //休眠1秒钟
}catch(InterruptedException e){
System.out.println("异常");
}
this.repaint(100);
}
}
public void paint(Graphics g){
Font f=new Font("宋体",Font.BOLD,16);
SimpleDateFormat SDF=new SimpleDateFormat("yyyy'年'MM'月'dd'日'HH:mm:ss");//格式化时间显示类型
Calendar now=Calendar.getInstance();
time=SDF.format(now.getTime()); //得到当前日期和时间
g.setFont(f);
g.setColor(Color.orange);
g.drawString(time,45,25);
}
}
首先，控制台输入肯定要是形如2013-03-06这样的格式，这是SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-DD")所要求的。输入2013-03会进入异常处理提示输入格式不正确。至于打印日历，你可以算出该月的第一号是星期几，然后按顺序排下去，满7天换行就是了