请问下面题目的运行结果是什么？为什么？

Question

public class Test {
    String str = "good";
    char[] ch = {'a','b','c'};
    public static void main(String[] args){
        Test t = new Test();
        t.change(t.str, t.ch);
        System.out.print(t.str+" and ");
        System.out.print(t.ch);
    }
    public void change(String str,char ch[]){
        str="test ok";
        ch[0]='g';
    }
}

Answer 1

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

Answer 2

String类比较特殊，创建对象后值不会改变，改变的只是地址的引用，那些新的string对象需要在堆中重新开辟内存空间，所以值的本身不会变，只是引用地址发生变化而已

Answer 3

运行结果：good and gbc涉及到作用域的问题，因为t是Test的对象，t.str指向的就是是类变量也就是good，方法里面的str为局部变量，如果在方法里输出str，就近原则则输出test ok，因为在方法里面没有重新声明ch，所以ch[0]被重新复制为g，要注意类变量是全局的，也就是你在这个类的任何地方都可以访问