diff --git a/src/main/java/me/ehlxr/powermock/ClassUnderTest.java b/src/main/java/me/ehlxr/powermock/ClassUnderTest.java
index 9a7ed00..1e785ea 100644
--- a/src/main/java/me/ehlxr/powermock/ClassUnderTest.java
+++ b/src/main/java/me/ehlxr/powermock/ClassUnderTest.java
@@ -3,7 +3,9 @@ package me.ehlxr.powermock;
 /**
  * Created by lixiangrong on 2017/11/3.
  */
+
 import java.io.File;
+
 /**
  * Created by lixiangrong on 2017/7/21.
  */
@@ -11,34 +13,43 @@ public class ClassUnderTest {
     public boolean callArgumentInstance(File file) {
         return file.exists();
     }
+
     public boolean callInternalInstance(String path) {
         File file = new File(path);
         return file.exists();
     }
+
     public boolean callFinalMethod(ClassDependency refer) {
         return refer.isAlive();
     }
+
     public boolean callSystemFinalMethod(String str) {
         return str.isEmpty();
     }
+
     public boolean callStaticMethod() {
         return ClassDependency.isExist();
     }
+
     public String callSystemStaticMethod(String str) {
         return System.getProperty(str);
     }
+
     public boolean callPrivateMethod() {
         return isExist();
     }
-    public boolean callVoidPrivateMethod(){
+
+    public boolean callVoidPrivateMethod() {
         testVoid();
         return true;
     }
+
     private boolean isExist() {
         // do something
         return false;
     }
-    private void testVoid(){
+
+    private void testVoid() {
         System.out.println("do nothing");
     }
 }
\ No newline at end of file
diff --git a/src/main/java/me/ehlxr/powermock/TestClassUnderTest.java b/src/main/java/me/ehlxr/powermock/TestClassUnderTest.java
index 197d04b..1a3bac0 100644
--- a/src/main/java/me/ehlxr/powermock/TestClassUnderTest.java
+++ b/src/main/java/me/ehlxr/powermock/TestClassUnderTest.java
@@ -9,8 +9,6 @@ import org.powermock.modules.junit4.PowerMockRunner;
 
 import java.io.File;
 
-import static org.mockito.ArgumentMatchers.anyString;
-
 /**
  * Created by lixiangrong on 2017/7/21.
  */
@@ -75,7 +73,7 @@ public class TestClassUnderTest {
     public void testCallPrivateMethod() throws Exception {
         ClassUnderTest underTest = PowerMockito.mock(ClassUnderTest.class);
         PowerMockito.when(underTest.callPrivateMethod()).thenCallRealMethod();
-        PowerMockito.when(underTest, "isExist", anyString()).thenReturn(true);
+        PowerMockito.when(underTest, "isExist").thenReturn(true);
         Assert.assertTrue(underTest.callPrivateMethod());
     }