java.lang.IllegalArgumentException:错误

报错内容：

D:\eclipse\workspace\Proxy/bin/com/sxw/simulationJdkProxy/$Proxy0.java

java.lang.IllegalArgumentException: argument type mismatch

at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

at java.lang.reflect.Constructor.newInstance(Constructor.java:423)

at com.sxw.simulationJdkProxy.Proxy.newProxyInstance(Proxy.java:77)

at com.sxw.simulationJdkProxy.Test.main(Test.java:7)

Exception in thread "main" java.lang.NullPointerException

at com.sxw.simulationJdkProxy.Test.main(Test.java:8)

代码部分：

//编译部分

//编译器

JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

//获取文件管理器

StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, null, null);

//获取文件

Iterable fileMag=fileManager.getJavaFileObjects(fileName);

//编译任务

CompilationTask task=compiler.getTask(null, fileManager, null, null, null, fileMag);

//进行编译

task.call();

fileManager.close();

//load到内存中

ClassLoader cl = ClassLoader.getSystemClassLoader();

Class class1 = cl.loadClass("com.sxw.simulationJdkProxy.$Proxy0");

//得到构造器，根据构造器创建对象

Constructor constructor =class1.getConstructor(interf);

return constructor.newInstance(new Car());