change code for ObjectUtil.isNotNull

hutool-core/src/main/java/cn/hutool/core/util/ObjectUtil.java

@@ -211,12 +211,17 @@ public class ObjectUtil {
 
 	/**
 	 * 检查对象是否不为null
+	 * <pre>
+	 * 1. != null
+	 * 2. not equals(null)
+	 * </pre>
 	 *
 	 * @param obj 对象
-	 * @return 是否为null
+	 * @return 是否为非null
 	 */
 	public static boolean isNotNull(Object obj) {
-		return false == isNull(obj);
+		//noinspection ConstantConditions
+		return null != obj && false == obj.equals(null);
 	}
 
 	/**
@@ -621,8 +626,8 @@ public class ObjectUtil {
 	 *
 	 * @param objs 被检查对象
 	 * @return 是否存在
-	 * @since 5.5.3
 	 * @see ArrayUtil#hasNull(Object[])
+	 * @since 5.5.3
 	 */
 	public static boolean hasNull(Object... objs) {
 		return ArrayUtil.hasNull(objs);

hutool-core/src/test/java/cn/hutool/core/util/ObjectUtilTest.java

@@ -93,4 +93,10 @@ public class ObjectUtilTest {
 		final boolean basicType = ObjectUtil.isBasicType(a);
 		Assert.assertTrue(basicType);
 	}
+
+	@Test
+	public void isNotNullTest(){
+		String a = null;
+		Assert.assertFalse(ObjectUtil.isNotNull(a));
+	}
 }