Duration和Period

src/chapter5/Example23.java

@@ -1,4 +1,19 @@
 package chapter5;
 
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+
 public class Example23 {
+    public static void main(String[] args) {
+        // 1. 获取当前时间
+        LocalDateTime now = LocalDateTime.now();
+        System.out.println("原格式：" + now);
+        System.out.println("只有日期：" + now.toLocalDate());
+        System.out.println("只有时间：" + now.toLocalTime());
+        // 2. getter 方法
+        System.out.println(now.getYear() +"年" + now.getMonthValue() + "月" + now.getDayOfMonth() + "号 "
+            + now.getHour() + "点" + now.getMinute() + "分" + now.getSecond() + "秒");
+        // 3. 指定格式
+        System.out.println("指定格式：" + now.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
+    }
 }

src/chapter5/Example24.java

@@ -0,0 +1,20 @@
+package chapter5;
+
+import java.time.Duration;
+import java.time.LocalTime;
+
+public class Example24 {
+    public static void main(String[] args) {
+        LocalTime start = LocalTime.now();
+        LocalTime end = LocalTime.of(21, 53, 0);
+
+        Duration duration = Duration.between(start, end);
+
+        System.out.println("时间间隔（纳秒）" + duration.toNanos());
+        System.out.println("时间间隔（毫秒）" + duration.toMillis());
+        System.out.println("时间间隔（秒）" + duration.toSeconds());
+        System.out.println("时间间隔（分钟）" + duration.toMinutes());
+        System.out.println("时间间隔（小时）" + duration.toHours());
+
+    }
+}

src/chapter5/Example25.java

@@ -0,0 +1,16 @@
+package chapter5;
+
+import java.time.LocalDate;
+import java.time.Period;
+
+public class Example25 {
+    public static void main(String[] args) {
+        LocalDate birthday = LocalDate.of(2018, 12, 12);
+        LocalDate now = LocalDate.of(2020, 11, 13);
+
+        Period period = Period.between(birthday, now);
+        System.out.println("时间间隔（年）" + period.getYears());
+        System.out.println("时间间隔（月）" + period.getMonths());
+        System.out.println("时间间隔（天）" + period.getDays());
+    }
+}

src/chapter5/demo55.java

@@ -0,0 +1,43 @@
+package chapter5;
+
+import java.time.LocalDate;
+import java.util.Scanner;
+
+public class demo55 {
+    public static void main(String[] args) {
+        Scanner scn = new Scanner(System.in);
+        System.out.println("请输入要判断的年份：");
+        int year = scn.nextInt();
+
+        System.out.println("方法一：" + year + "的2月有" + getNumOfDaysInFeb1(year) + "天");
+        System.out.println("方法二：" + year + "的2月有" + getNumOfDaysInFeb2(year) + "天");
+    }
+
+    /**
+     * 思路一
+     * @param year 年份
+     * @return 2月的天数
+     */
+    public static int getNumOfDaysInFeb1(int year) {
+        LocalDate date = LocalDate.of(year, 3, 1);
+        LocalDate feb = date.minusDays(1);
+        return feb.getDayOfMonth();
+    }
+
+    /**
+     * 思路二
+     * @param year 年份
+     * @return 2月的天数
+     */
+    public static int getNumOfDaysInFeb2(int year) {
+        LocalDate date = LocalDate.of(year, 1, 1);
+        if (date.isLeapYear()) {
+            return 29;
+        } else {
+            return 28;
+        }
+
+        // return date.isLeapYear() ? 29 : 28;
+    }
+
+}