4. The results indicate the following programs running:

The results indicate the following programs running:

public class Example{
    String str=new String("tarena");
    char[]ch={'a','b','c'};
    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[]){
   //引用类型变量，传递的是地址，属于引用传递。
        str="test ok";
        ch[0]='g';
    }
}

A.tarena and abc

B.tarena and gbc

C.test ok and abc

D.test ok and gbc

---

This title selected B.

string and char array is a reference type, a reference type is passed address will affect the value of the original variable, but string is a special reference type, why? Because the value of type string are immutable, in order to consider some memory, integrated security reasons, set it to immutable; immutable is how to achieve? Java in memory specifically for the string opened a string constant pool, used to lock the data is not tampered with, so the title str variable in the function and the original str is not a thing, it is a local reference, point to a testok string, with the end of the function, it is also nothing, but a char array will change the original value