小编kom*_*nan的帖子

public class InterfaceCasting {

    private static class A{}

    public static void main(String[] args) {
        A a = new A();
        Serializable serializable = new Serializable(){};
        a = (A)serializable;
    }

}

编译成功但运行时异常

Exception in thread "main" java.lang.ClassCastException: InterfaceCasting$1 cannot be cast to InterfaceCasting$A

为什么汇编成功？编译器必须知道serialiazable不是A？

问题来自http://www.javacertifications.net/javacert/scjp1.6Mock.jsp

问题没有-20

以下代码的输出是什么？

public class Test extends Thread
{   
    static String sName = "good";
    public static void main(String argv[])
    {
        Test t = new Test();
        t.nameTest(sName);
        System.out.println(sName);    
    }
    public void nameTest(String sName)
    {
        sName = sName + " idea ";
        start();
    }
    public void run()
    {
        for(int i=0;i  <  4; i++)
        {
            sName = sName + " " + i;

        }
    }
}

选项A)好B)好主意C)好主意好主意正确答案是:A

解释:在String的情况下,本地方法中的更改值不会在全局中更改(因为String对象是不可变的).