（1）
/**
* @author: sunshine
* @description:
* @data: 2022/2/28 20:56
* @version: 0.1
* @since: jdk11
*/
//1.将长时间格式时间转换为字符串 yyyy-MM-dd HH:mm:ss
public class Exercise1 {
public static void main(String[] args) {
demo1(); //(jdk1.8之前)
demo2(); //(jdk1.8之后)
}
private static void demo2() {
LocalDateTime localDateTime = LocalDateTime.of(2022,Calendar.FEBRUARY,1,12,0,0);
DateTimeFormatter formatter = DateTimeFormatter.ofPattern(PATTERN);
String format = formatter.format(localDateTime);
System.out.println(format);
//String format1 = localDateTime.format(formatter);
}
private static final String PATTERN = "yyyy-MM-dd HH:mm:ss";
private static void demo1() {
//Date转String
//1.创建Date对象
Date date = new Date(); //获得系统当前时间
long time = date.getTime(); //获得毫秒数（不推荐）
long millis = System.currentTimeMillis(); //推荐
//创建Calender对象
Calendar calendar = Calendar.getInstance();
calendar.set(2022,Calendar.FEBRUARY,1,12,0,0); //2022-2-1 12:00:00
//Calender转Date
Date date1 = calendar.getTime();
//2.创建格式类DateFormat
DateFormat dateFormat = new SimpleDateFormat(PATTERN);
String dateStr = dateFormat.format(date);
System.out.println(dateStr);
}
}
（2）
/**
* @author: sunshine
* @description:
* @data: 2022/2/28 21:22
* @version: 0.1
* @since: jdk11
*/
//2.使用Calendar类的相关属性以及方法！打印出某年某个月的日历信息！（要求年月日由命令行输入）
public class Exercise2 {
public static void main(String[] args) {
//demo3();
demo4();
}
private static void demo4() {
//动态月份的情况
int year = 2022;
Scanner input = new Scanner(System.in);
System.out.println("请录入月份:");
int month = input.nextInt();
Calendar calendar = Calendar.getInstance();
calendar.set(year,month-1,1);
System.out.println("日\t一\t二\t三\t四\t五\t六");
int totalDay = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
//判断1号有几个空格
int day = calendar.get(Calendar.DAY_OF_WEEK);
for (int i = 1; i < day; i++) {
System.out.print("\t");
}
for (int i = 1; i <= totalDay; i++) {
System.out.print(i+"\t");
//判断当前天是否为一周最后一天，是则换行
calendar.set(Calendar.DAY_OF_MONTH,i);
if (calendar.get(Calendar.DAY_OF_WEEK)==7){
System.out.println();
}
}
}
private static void demo3() {
//固定月份的情况
int year = 2022;
int month = 2;
Calendar calendar = Calendar.getInstance();
calendar.set(year,month-1,1); //2月份的序号是1
System.out.println("日\t一\t二\t三\t四\t五\t六");
int totalDay = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
System.out.print("\t\t");
for (int i = 1; i <= totalDay; i++) {
System.out.print(i+"\t");
//判断当前天是否为一周最后一天，是则换行
calendar.set(Calendar.DAY_OF_MONTH,i);
if (calendar.get(Calendar.DAY_OF_WEEK) == Calendar.SATURDAY){
System.out.println();
}
}
}
}
（3）
//4.计算两个时间相差几个小时
public class Exercise4 {
public static void main(String[] args) {
//demo1();
demo2();
}
private static void demo2() {
//LocalDateTime 与 LocalDateTime
LocalDateTime dateTime1 = LocalDateTime.of(2022,Calendar.FEBRUARY,1,12,0,0);
LocalDateTime dateTime2 = LocalDateTime.now();
long hours = dateTime1.until(dateTime2, ChronoUnit.HOURS); //括号里的减括号外面的
System.out.println(hours);
}
private static void demo1() {
//Date 与 Date
Calendar calendar = Calendar.getInstance();
calendar.set(2022,Calendar.FEBRUARY,1,12,0,0); //2022-2-1 12:00:00
Date date1 = calendar.getTime();
Date date2 = new Date();
long result = Math.abs((date1.getTime()-date2.getTime())/1000/3600);
System.out.println(result);
}
}
（4）
/**
* @author: sunshine
* @description:
* @data: 2022/2/28 21:24
* @version: 0.1
* @since: jdk11
*/
//5.一个方法，要求传入时间和间隔天数，返回新的日期
public class Exercise5 {
public static void main(String[] args) {
demo1(new Date(),10); //Date之间的操作
demo2(LocalDate.now(),10); //LocalDate之间的操作
}
private static LocalDate demo2(LocalDate localDate,int days) {
return localDate.plusDays(days);
}
private static Date demo1(Date date,int days) {
//传入时间加时间间隔
//用毫秒数来写
long time = date.getTime() + Duration.ofDays(days).toMillis(); //加号后面的是天转毫秒
return new Date(time);
}
}
（5）
/**
* @author: sunshine
* @description:
* @data: 2022/2/28 21:24
* @version: 0.1
* @since: jdk11
*/
//6.要求写一个工具类，可以自定义获取N个随机数字或字母（0~9,a~z,A~Z混合一起）
public class Exercise6 {
public static void main(String[] args) {
demo1();
//demo2();
}
private static void demo2() {
StringBuilder builder = new StringBuilder();
ThreadLocalRandom random = ThreadLocalRandom.current();
int choice = random.nextInt(0,3);
for (int i = 1; i <= 5; i++) {
char ch = ' ';
switch (choice) {
case 0:
ch = (char)random.nextInt(48,57);
break;
case 1:
ch = (char)random.nextInt(68,90);
break;
case 2:
ch = (char)random.nextInt(97,122);
break;
}
builder.append(ch);
}
System.out.println(builder.toString());
}
private static void demo1() {
//48-57 0-9 A-Z 65-90 a-z 97-122
ThreadLocalRandom random = ThreadLocalRandom.current();
StringBuilder builder = new StringBuilder();
int count = 5;
for(int i=1;i<=count;i++){
int num = random.nextInt(48,122);
if(num>=48 && num<=57){
num = num -48; //直接变成对应数字
builder.append(num);
}else if( (num>=65 && num<=90) || (num>=97 && num<=122) ){
char ch = (char)num; //数字转字符
builder.append(ch);
}else {
i--;
}
}
System.out.println(builder.toString());
}
}