Inner class

[Parameswaran Thangavel]

hi all
i just worked around some sample code and i just

pasted it, the doubt i got is given by the

commented line.just try explain its behaviour.


1)

class outer
{
outer()
{
System.out.println("outer constructor");
}
 
outer o=new outer();//[B]whts the reason "Stack over flow Exception"[/B]
 
                    // [B]is throwing[/B]
 
class inner
{
inner()
{
System.out.println("inner constructor");
}
 
public void innermethod()
{
System.out.println("outermethod");
}
 
}
 
public void outermethod()
{
System.out.println("outermethod");
}
public static void main(String argss[])
{
outer out=new outer();
outer.inner outinn=out.new inner();
 
}
 
}
 

2)

 
class outer
{
int y=2;
outer()
{
System.out.println("outer constructor");
}
static
{
int x;
outer o=new outer();
o.outermethod();
}
class inner
{
inner()
{
System.out.println("inner constructor");
}
 
public void innermethod()
{
outer oo=new outer();
oo.outermethod();
//System.out.println(outer.x);//[B]Both these line are[/B]
 
//System.out.println(outer.x);//[B]not working throwing error cant resolve[/B]
 
                               //[B]symbol properly[/B]
System.out.println(oo.y);
 
System.out.println("innerrmethod");
}
 
}
 
public void outermethod()
{
System.out.println("outermethod");
}
public static void main(String argss[])
{
outer out=new outer();
outer.inner outinn=out.new inner();
outinn.innermethod();
 
}
 
}
 

3)

class outer
{
int y=2;
outer()
{
System.out.println("outer constructor");
}
static
{
int x;
outer o=new outer();
o.outermethod();
}
class inner
{
inner()
{
System.out.println("inner constructor");
}
 
public void innermethod()
{
outer oo=new outer();
oo.outermethod();
 
oo.y=5;//[B]whats the difference between [/B]
System.out.println(outer.this.y);//[B]these two lines[/B]
System.out.println(oo.y);
 
System.out.println("innerrmethod");
}
 
}
 
public void outermethod()
{
System.out.println("outermethod");
}
public static void main(String argss[])
{
outer out=new outer();
outer.inner outinn=out.new inner();
outinn.innermethod();
 
}
 
}
 

4)

is it possible to use the this keyword inside the constructor

[Baiju Scariah]

I suggest you to study inner classes and ask doubt sepecifically rather than giving 3 or 4 programs and asking us to exaplin that...

[vidya sagar]

Hi paramesh

Code 1:

class stack
{
stack ss = new stack();
public static void main(String[] as)
{
new stack();
}
}

This normally throws stack overflow because when we create a object, JVM allocates space for reference ss and try to create a new space for its object, which it tends creates new space for its reference and try to assign its object for it...
so this way it going end up with a stack overflow error


In the code 2(part of your code)


static
{
int x;
outer o=new outer();
o.outermethod();
}

whenever a variable is declared in a block its scope ends when block ends



In the code 3(Part of your code)

public void innermethod()
{
outer oo=new outer(); //1
oo.outermethod(); //2
oo.y=5;//whats the difference between //3
System.out.println(outer.this.y);//these two lines // 4
System.out.println(oo.y); System.out.println("innerrmethod");
}


5 is instialized to value oo u created in line 2.
But outer.this.y refers to currently running object of outer class so it prints 2


4

Very well we can use this in constructor