关于java中的值传递与引用传递遇到的问题

来源于：https://www.nowcoder.com/test/question/done?tid=14302398&qid=25373#summary

下列java程序的输出结果为____。

 public class Example{
     String str=new String("hello");
     char[]ch={'a','b'};
     public static void main(String args[]){
         Example ex=new Example();
         ex.change(ex.str,ex.ch);
         System.out.print(ex.str+" and ");
         System.out.print(ex.ch);
     }
     public void change(String str,char ch[]){
         str="test ok";
         ch[0]='c';
     }
 }

正确答案: B   你的答案: E (错误)

hello and ab

hello and cb

hello and a

test ok and ab

test ok and cb

test ok and c