关于Java日期格式化及其使用例子

package com.gxa.jdk5.example15;
/**
 * 关于Java日期格式化及其使用例子
 */
import java.sql.ResultSet;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.DriverManager;
import java.sql.Timestamp;

import java.text.DecimalFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateFormatTest {
	
	private String user = "sa";
	private String password = "123456";
	private String url = "jdbc:microsoft:sqlserver://127.0.0.1:1433;DatabaseName=pubs";
	private static DateFormatTest dateFormatTest = null;
	
	private DateFormatTest() {
		try {
			Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
	
	public static synchronized DateFormatTest getInstance() {
		if (dateFormatTest == null) {
			return new DateFormatTest();
		}
		return dateFormatTest;
	}
	
	public Connection getConnection() {
		try {
			return DriverManager.getConnection(url, user, password);
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return null;
	}
	
	public void closeConn(Connection conn) {
		try {
			if (conn != null) {
				conn.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 显示Java日期格式化几个用例
	 *
	 */
	public void display_1() {
		//从字符串到日期类型的转换
		String date1 = "2009年09月09日";
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日");
		try {
			Date d = sdf.parse(date1);
			System.out.println("从字符串到日期类型的转换：" + d);
		} catch (ParseException e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 将日期类型转换成用户自定义形式
	 *
	 */
	public void display_2() {
		Date d = new Date();
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日");
		String strDate = sdf.format(d);
		System.out.println("将日期类型转换成用户自定义形式：" + strDate);
	}
	
	/**
	 * 在数据库里的日期只以年-月-日的方式输出
	 *
	 */
	public void display_3() {
		dateFormatTest = DateFormatTest.getInstance();
		Connection conn = dateFormatTest.getConnection();
		Statement stmt = null;
		ResultSet rs = null;
		String sql = "select * from employee";
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日");
		try {
			stmt = conn.createStatement();
			rs = stmt.executeQuery(sql);
			if (rs.next()) {
				System.out.println("存放数据库时间的形式：" + rs.getTimestamp("hire_date"));
				Timestamp timeStamp = rs.getTimestamp("hire_date");
				String strDate = sdf.format(new Date(timeStamp.getTime()));
				System.out.println("进行转换后的时间形式：" + strDate);
			}
			closeConn(conn);
			conn = null;
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 格式化小数
	 *
	 */
	public void display_4() {
		DecimalFormat df = new DecimalFormat(",###.00");  
		double aNumber = 33665448856.6568975;
		String result = df.format(aNumber);  
		System.out.println("格式化小数：" + result);
	}
	
	public static void main(String[] args) {
		dateFormatTest = DateFormatTest.getInstance();
		dateFormatTest.display_1();
		dateFormatTest.display_2();
		dateFormatTest.display_3();
		dateFormatTest.display_4();
	}

}