小编the*_*ant的帖子

在派生类构造函数中调用超类构造函数时,为什么id = 0的值？创建子对象时,何时在对象的堆中分配内存？基类构造函数运行之后或之前？

class Parent{
        int id = 10;
        Parent(){
            meth();
        }
        void meth(){
            System.out.println("Parent :"+ id);
        }
    }
    class Child extends Parent{
        int id = 5;
        Child(){
            meth();
        }
        void meth(){
            System.out.println("Child :"+ id);
        }
    }
    public class OverRidingEg {

        public static void main(String[] args) {
            // TODO Auto-generated method stub
            Child a= new Child();

        }

    }

我一直试图从数组中找到最大值.但我不断收到以下错误.请指教.

scores = [19212       56722       73336       44805       47268]

max(scores)

??? Index exceeds matrix dimensions.

我正在弄乱Eclipse上的JRE设置.最初项目设置为1.6,当设置为1.7时,我的程序开始显示很多错误.所以当我切换回1.6时,所有编译时错误都消失了,但我现在遇到了一个新问题.当我试图运行包含main函数的启动类时,这在控制台上显示..class文件都存在.请指教.

java.lang.UnsupportedClassVersionError: Demo : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(Unknown Source)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$000(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
Exception in thread "main" 

尝试创建用户名/密码验证表单.当我单击登录按钮即comamand1_click()时,收到以下错误"对象变量或未设置块变量".当我点击调试它指向

> rs.ActiveConnection = conn

我键入的代码:

Dim a
Dim conn As ADODB.Connection
Dim rs As ADODB.Recordset

Private Sub Command1_Click()
Set conn = New ADODB.Connection
conn.ConnectionString = "Provider = Microsoft.ACE.OLEDB.12.0; Data Source = C:\VB Project\logindetails1.mdb"
conn.Open

If conn = Null Then
    MsgBox ("no db")
    End
End If

rs.ActiveConnection = conn
rs.Source = "select * from login"
rs.Open

rs.MoveFirst
While Not rs.EOF
If Text1.Text = rs.Fields("id") And Text2.Text = rs.Fields("password") Then
    a = 1
Else
    a = 0
End If
Wend
rs.Close …