feat(utils): 添加自定义工具类

- 新增 Convert 类，提供类型转换方法
- 新增 JSONUtil 类，继承 JSON 工具类
- 新增 ObjectUtil 类，提供对象判断方法
- 新增 StrUtil 类，提供字符串常量

src/main/java/stu/utils/Convert.java

@@ -0,0 +1,25 @@
+package stu.utils;
+
+/**
+ * @Author cuiJiaWang
+ * @Create 2025-02-10 14:19
+ */
+public class Convert extends cn.hutool.core.convert.Convert {
+
+    /*
+        toStr
+        toInt
+     */
+
+    public static String toStr(Object value) {
+        return toStr(value, (String) null);
+    }
+
+    public static Integer toInt(Object value) {
+        return toInt(value, (Integer) null);
+    }
+
+    public static Integer toInt(Object value, Integer defaultValue) {
+        return (Integer) convertQuietly(Integer.class, value, defaultValue);
+    }
+}

src/main/java/stu/utils/JSONUtil.java

@@ -0,0 +1,9 @@
+package stu.utils;
+
+/**
+ * @Author cuiJiaWang
+ * @Create 2025-02-10 14:45
+ */
+public class JSONUtil extends cn.hutool.json.JSONUtil {
+
+}

src/main/java/stu/utils/ObjectUtil.java

@@ -0,0 +1,18 @@
+package stu.utils;
+
+/**
+ * @Author cuiJiaWang
+ * @Create 2025-02-10 14:22
+ */
+public class ObjectUtil extends cn.hutool.core.util.ObjectUtil{
+
+    public static void main(String[] args) {
+        Object obj = null;
+        ObjectUtil.isNull(obj);  // true
+        ObjectUtil.isEmpty(obj);  // true
+        obj = "";
+        ObjectUtil.isEmpty(obj);  // true
+        obj = " ";
+        System.out.println(ObjectUtil.isEmpty(obj));;  // false
+    }
+}

src/main/java/stu/utils/StrUtil.java

@@ -0,0 +1,17 @@
+package stu.utils;
+
+/**
+ * @Author cuiJiaWang
+ * @Create 2025-02-10 14:10
+ */
+public class StrUtil extends cn.hutool.core.util.StrUtil {
+    // cn.hutool.core.util.StrUtil extends CharSequenceUtil implements StrPool
+
+    /*
+        StrPool：":" ">" "{}" "\r" ...
+     */
+
+    public static void main(String[] args) {
+        System.out.println(StrUtil.COLON);   // :
+    }
+}