examplehub
diff --git a/src/main/java/com/examplehub/basics/number/DoubleExample.java b/src/main/java/com/examplehub/basics/number/DoubleExample.java
@@ -0,0 +1,4 @@
+package com.examplehub.basics.number;
+
+public class DoubleExample {
+}
diff --git a/src/main/java/com/examplehub/basics/oop/ObjectExample.java b/src/main/java/com/examplehub/basics/oop/ObjectExample.java
@@ -0,0 +1,4 @@
+package com.examplehub.basics.oop;
+
+public class ObjectExample {
+}
diff --git a/src/main/java/com/examplehub/leetcode/middle/ValidSudoku.java b/src/main/java/com/examplehub/leetcode/middle/ValidSudoku.java
@@ -29,7 +29,6 @@ public static boolean solution1(char[][] board) {
         return false;
       }
     }
-
     // travel all sub-box
     // TODO
     return true;

diff --git a/src/test/java/com/examplehub/basics/bool/BooleanExampleTest.java b/src/test/java/com/examplehub/basics/bool/BooleanExampleTest.java
@@ -48,4 +48,24 @@ void testTernaryOperator() {
     int abs = num < 0 ? -num : num;
     assertEquals(3, abs);
   }
+
+  @Test
+  void testValueOf() {
+    Boolean b = Boolean.valueOf(true);
+    assertTrue(b.booleanValue());
+
+    b = Boolean.valueOf("false");
+    assertFalse(b.booleanValue());
+  }
+
+  @Test
+  void testAutoBoxing() {
+    Boolean b = false;
+    System.out.println(b);
+    assertFalse(b);
+
+    boolean bValue = b;
+    System.out.println(bValue);
+    assertFalse(bValue);
+  }
 }
diff --git a/src/test/java/com/examplehub/basics/chars/CharExampleTest.java b/src/test/java/com/examplehub/basics/chars/CharExampleTest.java
@@ -32,4 +32,63 @@ void testAddAndSub() {
     assertEquals(9, '9' - '0');
     assertEquals(0, 'a' - 97);
   }
+
+  @Test
+  void testValueOf() {
+    Character c = Character.valueOf('A');
+    assertEquals('A', c.charValue());
+  }
+
+  @Test
+  void testAutoboxing() {
+    Character c = 'A';
+    System.out.println(c);
+    assertEquals('A', c);
+  }
+
+  @Test
+  void testIsLower() {
+    assertFalse(Character.isLowerCase('A'));
+    assertTrue(Character.isLowerCase('a'));
+    assertFalse(Character.isLowerCase('1'));
+  }
+
+  @Test
+  void testIsUpper() {
+    assertTrue(Character.isUpperCase('A'));
+    assertFalse(Character.isUpperCase('a'));
+    assertFalse(Character.isUpperCase('1'));
+  }
+
+  @Test
+  void testIsDigit() {
+    System.out.println(Character.isDigit('A'));
+    System.out.println(Character.isDigit('a'));
+    System.out.println(Character.isDigit('1'));
+
+    assertFalse(Character.isDigit('A'));
+    assertFalse(Character.isDigit('a'));
+    assertTrue(Character.isDigit('1'));
+  }
+
+  @Test
+  void testToLower() {
+    assertEquals('a', Character.toLowerCase('A'));
+  }
+
+  @Test
+  void testToUpper() {
+    assertEquals('A', Character.toUpperCase('a'));
+  }
+
+  @Test
+  void testGetNumericValue() {
+    System.out.println(Character.getNumericValue('8'));
+    assertEquals(8, Character.getNumericValue('8'));
+
+    System.out.println(Character.getNumericValue('A'));
+    System.out.println(Character.getNumericValue('a'));
+    assertEquals(10, Character.getNumericValue('A'));
+    assertEquals(10, Character.getNumericValue('a'));
+  }
 }
diff --git a/src/test/java/com/examplehub/basics/number/DoubleExampleTest.java b/src/test/java/com/examplehub/basics/number/DoubleExampleTest.java
@@ -0,0 +1,32 @@
+package com.examplehub.basics.number;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class DoubleExampleTest {
+  @Test
+  void testValueOf() {
+    Double d = Double.valueOf(3.14);
+    System.out.println(d.doubleValue());
+    assertEquals(3.14, d.doubleValue());
+
+    d = Double.valueOf("3.14159");
+    System.out.println(d.doubleValue());
+    assertEquals(3.14159, d.doubleValue());
+  }
+
+  @Test
+  void testIsNaN() {
+    Double d = 0.0 / 0;
+    assertEquals(d, Double.NaN);
+  }
+
+  @Test
+  void testAutoboxing() {
+    Double d = 3.14;
+    assertEquals(3.14, d.doubleValue());
+    double pi = d;
+    assertEquals(3.14, pi);
+  }
+}
diff --git a/src/test/java/com/examplehub/basics/number/IntegerExampleTest.java b/src/test/java/com/examplehub/basics/number/IntegerExampleTest.java
@@ -2,16 +2,51 @@
 
 import static org.junit.jupiter.api.Assertions.*;
 
+import jdk.jfr.StackTrace;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.function.Executable;
 
 class IntegerExampleTest {
+
+  @Test
+  void testValueOf() {
+    Integer integer = Integer.valueOf(100);
+    System.out.println(integer);
+    assertEquals(100, integer.intValue());
+
+    integer = Integer.valueOf("123");
+    System.out.println(integer);
+    assertEquals(123, integer.intValue());
+
+    integer = Integer.valueOf("a", 16);
+    System.out.println(integer);
+    assertEquals(10, integer.intValue());
+  }
+
+  @Test
+  void testParseInt() {
+    int number = Integer.parseInt("123");
+    System.out.println(number);
+    assertEquals(123, number);
+
+    assertThrows(NumberFormatException.class, () -> {
+      int num = Integer.parseInt("123a");
+      fail();
+    });
+  }
+
   @Test
   void testAutoBoxing() {
     Integer integer = 10;
     assertEquals(10, integer.intValue());
     Integer integer1 = 10;
     assertTrue(integer == integer1);
     assertTrue(integer.equals(integer1));
+
+    Integer first = 128;
+    Integer second = 128;
+    System.out.println(first == second);
+    assertNotSame(first, second);
   }
 
   @Test
@@ -24,4 +59,19 @@ void testAutoBoxingNullPointer() {
       assertTrue(true);
     }
   }
+
+  @Test
+  void testToBinaryString() {
+    assertEquals("1010", Integer.toBinaryString(10));
+  }
+
+  @Test
+  void testToOctalString() {
+    assertEquals("12", Integer.toOctalString(10));
+  }
+
+  @Test
+  void test(){
+    assertEquals("a", Integer.toHexString(10));
+  }
 }
diff --git a/src/test/java/com/examplehub/basics/oop/ObjectExampleTest.java b/src/test/java/com/examplehub/basics/oop/ObjectExampleTest.java
@@ -0,0 +1,110 @@
+package com.examplehub.basics.oop;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Objects;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ObjectExampleTest {
+  @Test
+  void testObject() {
+    Object o = new Object();
+    System.out.println(o);
+  }
+
+  @Test
+  void testEquals() {
+    class Student {
+      private int id;
+      private String name;
+      public Student(int id, String name) {
+        this.id = id;
+        this.name = name;
+      }
+    }
+    class People {
+      private final String name;
+      private final int age;
+
+      public People(String name, int age) {
+        this.name = name;
+        this.age = age;
+      }
+
+      @Override
+      public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        People people = (People) o;
+        return age == people.age && Objects.equals(name, people.name);
+      }
+
+      @Override
+      public int hashCode() {
+        return 0;
+      }
+    }
+    Student stu1 = new Student(10001, "duyuanchao");
+    Student stu2 = new Student(10001, "duyuanchao");
+    assertNotSame(stu1, stu2);
+    assertNotEquals(stu1, stu2);
+
+    People p1 = new People("duyuanchao", 25);
+    People p2 = new People("duyuanchao", 25);
+    People p3 = new People("jack", 25);
+    assertNotSame(p1, p2);
+    assertEquals(p1, p2);
+    assertNotEquals(p1, p3);
+  }
+
+  @Test
+  void testHashCode() {
+    class People {
+      private final String name;
+      private final int age;
+
+      public People(String name, int age) {
+        this.name = name;
+        this.age = age;
+      }
+
+      @Override
+      public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        People people = (People) o;
+        return age == people.age && Objects.equals(name, people.name);
+      }
+
+      @Override
+      public int hashCode() {
+        return this.age % 13;
+      }
+    }
+    People p1 = new People("duyuanchao", 25);
+    People p2 = new People("duyuanchao", 25);
+    assertEquals(p1.hashCode(), p2.hashCode());
+  }
+
+  @Test
+  void testToString() {
+    class People {
+      private final String name;
+      private final int age;
+
+      public People(String name, int age) {
+        this.name = name;
+        this.age = age;
+      }
+
+      @Override
+      public String toString() {
+        return "name = " + name + ", age = " + age;
+      }
+    }
+
+    People people = new People("duyuanchao", 25);
+    assertEquals("name = duyuanchao, age = 25", people.toString());
+  }
+}
diff --git a/src/test/java/com/examplehub/basics/utils/MathUtilsExampleTest.java b/src/test/java/com/examplehub/basics/utils/MathUtilsExampleTest.java
@@ -51,4 +51,11 @@ void testRandom() {
     double randomNumber = Math.random();
     assertTrue(randomNumber >= 0 && randomNumber < 1);
   }
+
+  @Test
+  void testRound() {
+    assertEquals(3, Math.round(3.14));
+    assertEquals(4, Math.round(3.78));
+    assertEquals(-3, Math.round(-3.14));
+  }
 }
-Original file line number
+Diff line change
@@ Expand Up / @@ -29,7 +29,6 @@ public static boolean solution1(char[][] board) { @@
             return false;
           }
         }
         // travel all sub-box
         // TODO
         return true;
@@ Expand Down @@