小编beg*_*ner的帖子

我不明白为什么Constructor call must be the first statement in a constructor如果我转移this(1);到构造函数中的最后一行,下面的代码显示错误.

package learn.basic.corejava;

public class A {
    int x,y;

    A()
    {     
        // this(1);// ->> works fine if written here
        System.out.println("1");
        this(1);  //Error: Constructor call must be the first statement in a constructor
    }

    A(int a)
    {
        System.out.println("2");
    }

    public static void main(String[] args) { 
        A obj1=new A(2);  
    }   
}

我在StackOverflow上检查了很多关于这个主题的答案,但我仍然无法理解这个原因.请帮我用一些简单的例子和​​解释来说明这个错误.

我尝试使用<s:url ..标记实现令牌拦截器,但在第一次单击时显示错误.即The form has already been processed or no token was supplied, please try again.

我想实现这个拦截器,因为如果用户已经删除了一行并再次刷新页面,那么同一个动作不应该再次执行.

<s:url id="linkdelete" action="DeleteLatestUpload.action" namespace="/admin/insecure/upload">
     <s:param name="latestUploadId" value="latestUploadId"></s:param>
     <s:token name="token"></s:token>
</s:url> 
<a href='<s:property value="#linkdelete"/>' style="color: white;text-decoration:  none;" class="delbuttonlink">Clear current Uploads</a>

和我的struts.xml:

 <action name="DeleteLatestUpload" class="v.esoft.actions.UploadExcel" method="deleteUploads">                   
     <interceptor-ref name="token"></interceptor-ref>
     <interceptor-ref name="basicStack"></interceptor-ref>  
     <result name="success" type="tiles"> uploadforward</result>
     <result name="invalid.token" type="tiles">uploadforward </result>
 </action>

假设我有一个当前的网址显示 http://localhost.com/welcome/blah_blah,从这个网址我希望只能http://localhost.com/ 进入一个页面.

这该怎么做？？

我知道echo current_url();给出了完整的网址.但我只想要http://localhost.com排除controller_name,clasname等.

预期产出

如果我的base_url = http://www.exaple.com/folder¤t_url = http://exaple.com/folder/class/method/blah_blah,那么我想要的域名exaple.com不是www.exaple.com !

我正面临一个问题.

正如我所知,构造函数,Instance Initialization块不会继承到子类,但是下面的代码继承了超类构造函数,它为什么要调用？

预期的产出是:来自缺点2

但它的显示输出如下:--IIB--来自cons 2来自cons 2

WHY? this output , *As i know "sub class should not inherit Constructor & IIB block"* 

请帮我弄清楚这个概念.

public class X
{ 
    {
        System.out.println("--IIB--");
    }       

    X()
    {
        System.out.println("from cons 1");
    }
}   

class Y extends X
{
     Y()
     {
         System.out.print("from cons 2");
     }
}    


class Z 
{
    public static void main(String args[])
    {
        Y ob=new Y(); 
    }
}