code simplify

Author: wuwen5

src/main/java/org/apache/ibatis/reflection/property/PropertyNamer.java

@@ -15,7 +15,7 @@
  */
 package org.apache.ibatis.reflection.property;
 
-import java.util.Locale;
+import java.beans.Introspector;
 
 import org.apache.ibatis.reflection.ReflectionException;
 
@@ -37,11 +37,7 @@ public static String methodToProperty(String name) {
       throw new ReflectionException("Error parsing property name '" + name + "'.  Didn't start with 'is', 'get' or 'set'.");
     }
 
-    if (name.length() == 1 || (name.length() > 1 && !Character.isUpperCase(name.charAt(1)))) {
-      name = name.substring(0, 1).toLowerCase(Locale.ENGLISH) + name.substring(1);
-    }
-
-    return name;
+    return Introspector.decapitalize(name);
   }
 
   public static boolean isProperty(String name) {

src/test/java/org/apache/ibatis/reflection/property/PropertyNamerTest.java

@@ -0,0 +1,22 @@
+package org.apache.ibatis.reflection.property;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class PropertyNamerTest {
+
+  @Test
+  void methodToProperty() {
+    assertEquals("ok", PropertyNamer.methodToProperty("isOk"));
+    assertEquals("OK", PropertyNamer.methodToProperty("isOK"));
+
+    assertEquals("name", PropertyNamer.methodToProperty("getName"));
+    assertEquals("XName", PropertyNamer.methodToProperty("getXName"));
+    assertEquals("xName", PropertyNamer.methodToProperty("getxName"));
+
+    assertEquals("name", PropertyNamer.methodToProperty("setName"));
+    assertEquals("XName", PropertyNamer.methodToProperty("setXName"));
+    assertEquals("xName", PropertyNamer.methodToProperty("setxName"));
+  }
+}