关于constructor的一句话？？

[chl326]

the default constructor initializes the instance variables declared in the claaa

[chl326]

the default constructor initializes the instance variables declared in the class..
这句话对不？？

[yhc0125]

关注

[0legend]

找到个相关例子：//括号内是和例子相关的
We give our class instance variables to support reading from and writing to （socket streams）, and to （store details of the remote host to which we will connect0.

The constructor for our class （takes an IP address and a port number for a remote host and assigns them） to instance variables.

我想答案是肯定的了。

[0legend]

public class Sub extends Super{


public Sub(){
super(3);
}

public static void main(String[] args)
{
Sub test = new Sub();
}

}

// sub have no default constructor.

[wangtaoyy]

请看：
public class A
{
int b;
int a = 1
int c;
public A(int b){
this.b = b;
}
}

A test = new A(2);
没有default constructor但是test.a,和test.c都被正确初始化，
而且test.a不是default value .

[0legend]

default constructor can initialize instance variables but when u use the
variable ,it will get the value u give it.
if u and the default constructor all don't initialize instance variables
how can u use the instance variables not initialized ?

[wangtaoyy]

有一个叫initialize的动作完成initialize instance variables 而不是
default constructor

[0legend]

c & d

[contributor]

Default constructor CAN initialize the instance variables declared in the class. However, it CANNOT do it if you doesn't write the expression of the assignment in the default constructor. Therefore, the statements is not 100% right, only partially.

[binghuodao]

当然对

[chl326]

请看http://go2.163.com/chl886/qq35.gif(关于constructor )
我认为选ce
各位怎么看？？？

[contributor]

You are right!
Answer: C and E.

[0legend]

看来俺又错了，能在下面问个问题么？
Default constructor do need the instance variables initialized when the class compiled ?

[contributor]

I don't quit understand your question.
Default constructor can be empty when the class compiled.

[0legend]

thx.it means that it can do nothing and need nothing.

[contributor]

Yes! if you doesn't use default constructor to create new instance. However, default constructor can still be used to create new instance even if it has nothing.

[wangtaoyy]

不对
instance variable不是在constructor中初始化的
反证：如果instance variable在Default constructor中初始化
那么如果使用其它constructor导致instance variable不被初始化

[0legend]

but the default constructor initializes the variables to default value
//come from Core Java 2,Volume I :Fundamentals
Writer : Cay S.Horstmann && Gray Cornell

[chl326]

转帖
the default constructor invokes the no-parameter constructor of the superclasss说得不完全对。
public class Super{
public Super(){}

public Super(int i){
System.println(i);
}
}

public class Sub{

public Sub(){
Super(3);
}
}

[chl326]

抱歉，刚刚的例子有太多问题，你看看下面的。
class Super{
public Super(){
System.out.println("default");
}

public Super(int i){
System.out.println("none default");
}
}

public class Sub extends Super{


public Sub(){
super(3);
}

public static void main(String[] args)
{
Sub test = new Sub();
}

}

输出是：none default