请教几种常用函数的方法，如下

Java的一些常用函数,方法总结：1:数组方面:数组是一个对象,数组名可以理解和C++里面一样,1):System.arraycopy(src,srcindex,dst,dstindex,src.length);2):java.util.Arrays.sort(数组名);//块数排序法进行排序3):java.util.Arrays.binarySearch(arr,key);//从哪里收,关键值,返回索引.没有的话返回-14):java.util.Array.fill(arr,value),设置数组初始值5):Array.equals(arr1,arr2)//比较两个数组中元素是不是全部相等,是返回true,不是返回false2:时间方面:public static String dateToStr(java.util.Date date){SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");String str = sdf.format(date);return str;}import java.text.SimpleDateFormat;import java.util.Calendar;public class DateUtil{public static java.util.Date parseDate(String dateStr, String format){java.util.Date date = null;try{java.text.DateFormat df = new java.text.SimpleDateFormat(format);String dt = dateStr.replaceAll("-", "/");if ((!dt.equals("")) && (dt.length() < format.length())){dt += format.substring(dt.length()).replaceAll("[YyMmDdHhSs]", "0");}date = (java.util.Date) df.parse(dt);}catch (Exception e){}return date;}public static java.util.Date parseDate(String dateStr){return parseDate(dateStr, "yyyy/MM/dd");}public static String format(java.util.Date date, String format){String result = "";try{if (date != null){java.text.DateFormat df = new java.text.SimpleDateFormat(format);result = df.format(date);}}catch (Exception e){}return result;}public static String format(java.util.Date date){return format(date, "yyyy/MM/dd");}public static int getYear(java.util.Date date){java.util.Calendar c = java.util.Calendar.getInstance();c.setTime(date);return c.get(java.util.Calendar.YEAR);}public static int getMonth(java.util.Date date){java.util.Calendar c = java.util.Calendar.getInstance();c.setTime(date);return c.get(java.util.Calendar.MONTH) + 1;}public static int getDay(java.util.Date date){java.util.Calendar c = java.util.Calendar.getInstance();c.setTime(date);return c.get(java.util.Calendar.DAY_OF_MONTH);}public static int getHour(java.util.Date date){java.util.Calendar c = java.util.Calendar.getInstance();c.setTime(date);return c.get(java.util.Calendar.HOUR_OF_DAY);}public static int getMinute(java.util.Date date){java.util.Calendar c = java.util.Calendar.getInstance();c.setTime(date);return c.get(java.util.Calendar.MINUTE);}public static int getSecond(java.util.Date date){java.util.Calendar c = java.util.Calendar.getInstance();c.setTime(date);return c.get(java.util.Calendar.SECOND);}public static long getMillis(java.util.Date date){java.util.Calendar c = java.util.Calendar.getInstance();c.setTime(date);return c.getTimeInMillis();}public static String getDate(java.util.Date date){return format(date, "yyyy/MM/dd");}public static String getTime(java.util.Date date){return format(date, "HH:mm:ss");}public static String getDateTime(java.util.Date date){return format(date, "yyyy/MM/dd HH:mm:ss");}public static java.util.Date addDate(java.util.Date date, int day){java.util.Calendar c = java.util.Calendar.getInstance();c.setTimeInMillis(getMillis(date) + ((long) day) * 24 * 3600 * 1000);return c.getTime();}public static int diffDate(java.util.Date date, java.util.Date date1){return (int) ((getMillis(date) - getMillis(date1)) / (24 * 3600 * 1000));}public static String getMonthBegin(String strdate){java.util.Date date = parseDate(strdate);return format(date, "yyyy-MM") + "-01";}public static String getMonthEnd(String strdate){java.util.Date date = parseDate(getMonthBegin(strdate));Calendar calendar = Calendar.getInstance();calendar.setTime(date);calendar.add(Calendar.MONTH, 1);calendar.add(Calendar.DAY_OF_YEAR, -1);return formatDate(calendar.getTime());}public static String formatDate(java.util.Date date){return formatDateByFormat(date, "yyyy-MM-dd");}public static String formatDateByFormat(java.util.Date date, String format){String result = "";if (date != null){try{SimpleDateFormat sdf = new SimpleDateFormat(format);result = sdf.format(date);}catch (Exception ex){ex.printStackTrace();}}return result;}}Java日期格式化及其使用例子1 SimpleDateFormat担当重任,怎样格式化都行import java.util.Date;import java.text.SimpleDateFormat;public class Demo{public static void main(String[] args){Date now=new Date();SimpleDateFormat f=newSimpleDateFormat("今天是"+"yyyy年MM月dd日 E kk点mm分");System.out.println(f.format(now));f=new SimpleDateFormat("a hh点mm分ss秒");System.out.println(f.format(now));}}2 从字符串到日期类型的转换：import java.util.Date;import java.text.SimpleDateFormat;import java.util.GregorianCalendar;import java.text.*;publicclass Demo{public static void main(String[] args){String strDate="2005年04月22日";//注意：SimpleDateFormat构造函数的样式与strDate的样式必须相符SimpleDateFormat simpleDateFormat=new SimpleDateFormat("yyyy年MM月dd日");//必须捕获异常try{Date date=simpleDateFormat.parse(strDate);System.out.println(date);}catch(ParseException px){px.printStackTrace();}}}3 将毫秒数换转成日期类型import java.util.Date;import java.text.SimpleDateFormat;import java.util.GregorianCalendar;import java.text.*;public class Demo{public static void main(String[] args){long now=System.currentTimeMillis();System.out.println("毫秒数："+now);Date dNow=new Date(now);System.out.println("日期类型："+dNow);}}4 获取系统时期和时间，转换成SQL格式后更新到数据库java.util.Date d=new java.util.Date(); //获取当前系统的时间//格式化日期new java.text.SimpleDateFormat s= new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss");String dateStr = s.format(d); //转为字符串使用RS更新数据库，仍然要用rs.updateString，而不是rs.updateDade。rs.updateString("regtime",dateStr); //regtime字段为datetime类型的5 按本地时区输出当前日期Date myDate = new Date();System.out.println(myDate.toLocaleString());输出结果为：2003-5-306 如何格式化小数DecimalFormat df = new DecimalFormat(",###.00"); double aNumber = 33665448856.6568975;String result = df.format(aNumber); Sytem. out.println(result);输出结果为：33,665,448,856.66其他：获取毫秒时间 System.currentTimeMillis();7 在数据库里的日期只以年-月-日的方式输出定义日期格式：SimpleDateFormat sdf = new SimpleDateFormat(yy-MM-dd);sql语句为：String sqlStr = "select bookDate from roomBook where bookDate between '2007-4-10' and '2007-4-25'";输出：System.out.println(df.format(rs.getDate("bookDate"))); 

请教几种常用函数的方法，如下

2回答