update string and time utils usage

src/main/java/com/examplehub/basics/system/SystemExample.java

@@ -0,0 +1,4 @@
+package com.examplehub.basics.system;
+
+public class SystemExample {
+}

src/main/java/com/examplehub/basics/time/DateTimeFormatExample.java

@@ -0,0 +1,4 @@
+package com.examplehub.basics.time;
+
+public class DateTimeFormatExample {
+}

src/test/java/com/examplehub/basics/chars/StringBuilderExampleTest.java

@@ -5,23 +5,101 @@
 import org.junit.jupiter.api.Test;
 
 class StringBuilderExampleTest {
+
+  @Test
+  void testToString() {
+    StringBuilder builder = new StringBuilder("hello123");
+    assertEquals("hello123", builder.toString());
+  }
+  @Test
+  void testCapacity() {
+    StringBuilder sb = new StringBuilder();
+    assertEquals(16, sb.capacity());
+
+    sb = new StringBuilder(20);
+    assertEquals(20, sb.capacity());
+
+    sb = new StringBuilder("abc123");
+    assertEquals(22, sb.capacity());
+  }
+
   @Test
   void testAppend() {
-    StringBuilder builder = new StringBuilder();
-    builder.append("Hello").append(",").append("World").append("!");
-    assertEquals("Hello,World!", builder.toString());
+      StringBuilder builder = new StringBuilder();
+      builder.append("Hello").append(",").append("World").append("!");
+      assertEquals("Hello,World!", builder.toString());
+  }
+
+  @Test
+  void testInsert() {
+    StringBuilder builder = new StringBuilder("abc");
+    builder.insert(0, "123");
+    assertEquals("123abc", builder.toString());
+    builder.insert(3, "45");
+    assertEquals("12345abc", builder.toString());
+    builder.insert(builder.length(), "!");
+    assertEquals("12345abc!", builder.toString());
+  }
+
+  @Test
+  void testDeleteCharAt() {
+    StringBuilder builder = new StringBuilder("hello123abc");
+    builder.deleteCharAt(0);
+    assertEquals("ello123abc", builder.toString());
+
+    //delete ello
+    for (int i = 1; i <= 4; i++) {
+      builder.deleteCharAt(0);
+    }
+    assertEquals("123abc", builder.toString());
+    builder.deleteCharAt(builder.length() - 1);
+    assertEquals("123ab", builder.toString());
   }
 
   @Test
-  void testInitCapacity() {
-    String firstStr = "123456789";
-    String secondStr = "987654321";
-    String thirdStr = "abcef";
+  void testDelete() {
+    StringBuilder builder = new StringBuilder("123abcABC");
+    builder.delete(0, 3); // delete "123"
+    assertEquals("abcABC", builder.toString());
+    builder.delete(3, builder.length()); // delete "ABC"
+    assertEquals("abc", builder.toString());
+  }
+
+  @Test
+  void testCharAt() {
+    StringBuilder builder = new StringBuilder("0123456789abc");
+    assertEquals('a', builder.charAt(10));
+
+    for (int i = 0; i <= 9; ++i) {
+      assertEquals('0' + i, builder.charAt(i));
+    }
+  }
+
+  @Test
+  void testSetCharAt() {
+    StringBuilder builder = new StringBuilder("abC123");
+    builder.setCharAt(2, 'c');
+    assertEquals("abc123", builder.toString());
+  }
 
-    StringBuilder builder =
-        new StringBuilder(firstStr.length() + secondStr.length() + thirdStr.length());
-    assertEquals(
-        "123456789987654321abcef",
-        builder.append(firstStr).append(secondStr).append(thirdStr).toString());
+  @Test
+  void testReplace() {
+    StringBuilder builder = new StringBuilder("abc123");
+    builder.replace(0, 3, "ABC");
+    assertEquals("ABC123", builder.toString());
+  }
+
+  @Test
+  void testIndexOf() {
+    StringBuilder builder = new StringBuilder("abc123abc");
+    assertEquals(1, builder.indexOf("bc"));
+    assertEquals(7, builder.indexOf("bc", 3));
+  }
+
+  @Test
+  void testLastIndexOf() {
+    StringBuilder builder = new StringBuilder("abc123abc");
+    assertEquals(7, builder.lastIndexOf("bc"));
+    assertEquals(6, builder.lastIndexOf("abc", 6));
   }
 }

src/test/java/com/examplehub/basics/system/SystemExampleTest.java

@@ -0,0 +1,19 @@
+package com.examplehub.basics.system;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class SystemExampleTest {
+  @Test
+  void testCurrentTime() {
+    long startTime = System.currentTimeMillis();
+    int sum = 0;
+    for (int i = 1; i <= 100; ++i) {
+      sum += i;
+    }
+    assertEquals(5050, sum);
+    long endTime = System.currentTimeMillis();
+    assertTrue(endTime >= startTime);
+  }
+}

src/test/java/com/examplehub/basics/time/CalendarExampleTest.java

@@ -1,10 +1,22 @@
 package com.examplehub.basics.time;
 
+import org.junit.jupiter.api.Test;
+
 import java.text.SimpleDateFormat;
 import java.util.Calendar;
-import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
 
 class CalendarExampleTest {
+
+  @Test
+  void testInit() {
+    Calendar calendar = Calendar.getInstance();
+    calendar.set(2099, Calendar.DECEMBER, 31, 23, 59, 59);
+    assertEquals("2099-12-31 23:59:59",
+            new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(calendar.getTime()));
+  }
+
   @Test
   void test() {
     Calendar calendar = Calendar.getInstance();
@@ -30,6 +42,24 @@ void testSetCustomTime() {
     calendar.set(Calendar.HOUR_OF_DAY, 16);
     calendar.set(Calendar.MINUTE, 33);
     calendar.set(Calendar.SECOND, 59);
-    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(calendar.getTime()));
+
+    assertEquals("2088-09-25 16:33:59",
+            new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(calendar.getTime()));
+  }
+
+  @Test
+  void testAddField() {
+    Calendar calendar = Calendar.getInstance();
+    calendar.clear();
+    calendar.set(Calendar.YEAR, 2088);
+    calendar.set(Calendar.MONTH, 8);
+    calendar.set(Calendar.DATE, 25);
+    calendar.set(Calendar.HOUR_OF_DAY, 16);
+    calendar.set(Calendar.MINUTE, 33);
+    calendar.set(Calendar.SECOND, 59);
+
+    calendar.add(Calendar.YEAR, 12);
+    assertEquals("2100-09-25 16:33:59",
+            new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(calendar.getTime()));
   }
 }

src/test/java/com/examplehub/basics/time/DateExampleTest.java

@@ -1,10 +1,36 @@
 package com.examplehub.basics.time;
 
+import org.junit.jupiter.api.Test;
+
+import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.util.Date;
-import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 class DateExampleTest {
+
+  @Test
+  void testInit() {
+    Date firstDate = new Date();
+    Date secondDate = new Date(System.currentTimeMillis());
+    assertEquals(firstDate, secondDate);
+  }
+
+  @Test
+  void testGetTime() {
+    Date date = new Date(1636200610202L);
+    assertEquals(1636200610202L, date.getTime());
+  }
+
+  @Test
+  void testSetTime() {
+    long time = System.currentTimeMillis();
+    Date date = new Date(time);
+    assertEquals(time, date.getTime());
+  }
+
   @Test
   void test() {
     Date date = new Date();
@@ -19,6 +45,16 @@ void test() {
   @Test
   void testSimpleDateForMate() {
     SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
-    System.out.println(format.format(new Date()));
+    long time = 1636201275057L;
+    Date date = new Date(time);
+    String formatDate = format.format(date);
+    assertTrue("2021-11-06 20:21:15".equals(formatDate) || "2021-11-06 12:21:15".equals(formatDate));
+  }
+
+  @Test
+  void testParse() throws ParseException {
+    SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
+    long time = format.parse("2021-11-06 20:21:15").getTime();
+//    assertEquals(1636201275057L, time); TODO
   }
 }

src/test/java/com/examplehub/basics/time/DateTimeFormatExampleTest.java

@@ -0,0 +1,18 @@
+package com.examplehub.basics.time;
+
+import org.junit.jupiter.api.Test;
+
+import java.time.LocalDateTime;
+import java.time.Month;
+import java.time.format.DateTimeFormatter;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class DateTimeFormatExampleTest {
+  @Test
+  void test() {
+    LocalDateTime localDateTime = LocalDateTime.of(2099, Month.DECEMBER, 30, 23, 59, 59);
+    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
+    assertEquals("2099-12-30 23:59:59", formatter.format(localDateTime));
+  }
+}

src/test/java/com/examplehub/basics/time/LocalDateTimeExampleTest.java

@@ -4,10 +4,11 @@
 import java.time.LocalDateTime;
 import java.time.LocalTime;
 import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
 
 class LocalDateTimeExampleTest {
   @Test
-  void test() {
+  void testInit() {
     LocalDate localDate = LocalDate.now();
     LocalTime localTime = LocalTime.now();
     LocalDateTime localDateTime = LocalDateTime.now();
@@ -16,25 +17,26 @@ void test() {
     System.out.println("localDateTime: " + localDateTime);
   }
 
-  @Test
-  void test2() {
-    LocalDateTime localDateTime = LocalDateTime.now();
-    LocalDate localDate = localDateTime.toLocalDate();
-    LocalTime localTime = localDateTime.toLocalTime();
-    System.out.println("localDate: " + localDate);
-    System.out.println("localTime: " + localTime);
-    System.out.println("localDateTime: " + localDateTime);
-  }
 
   @Test
-  void test3() {
-    LocalDate d2 = LocalDate.of(2019, 11, 30);
-    LocalTime t2 = LocalTime.of(15, 16, 17);
-    LocalDateTime dt2 = LocalDateTime.of(2019, 11, 30, 15, 16, 17);
-    LocalDateTime dt3 = LocalDateTime.of(d2, t2);
-    System.out.println(d2);
-    System.out.println(t2);
-    System.out.println(dt2);
-    System.out.println(dt3);
+  void testOf() {
+    LocalDate localDate = LocalDate.of(2019, 11, 30);
+    LocalTime localTime = LocalTime.of(15, 16, 17);
+    LocalDateTime localDateTime = LocalDateTime.of(2019, 11, 30, 15, 16, 17);
+
+    assertEquals(2019, localDate.getYear());
+    assertEquals(11, localDate.getMonth().getValue());
+    assertEquals(30, localDate.getDayOfMonth());
+
+    assertEquals(15, localTime.getHour());
+    assertEquals(16, localTime.getMinute());
+    assertEquals(17, localTime.getSecond());
+
+    assertEquals(2019, localDateTime.getYear());
+    assertEquals(11, localDateTime.getMonthValue());
+    assertEquals(30, localDateTime.getDayOfMonth());
+    assertEquals(15, localDateTime.getHour());
+    assertEquals(16, localDateTime.getMinute());
+    assertEquals(17, localDateTime.getSecond());
   }
 }