why constructer for abstract class?

[santhosh.R gowda]

As we know abstract classes can never be instantiated .then what is the use of building the constructer by the compiler during copilation of abstract class
for example if i declare my abstract class

  

abstract  class abstractsuper
{
	public int i=10;
}
 

when i decompile my class file..

 
abstract class abstractsuper
{

    public int i;

    abstractsuper()
    {
        i = 10;
    }
}
       
 

please clear my doubt

[Maneesh Godbole]

Constructors in abstract classes are typically used, when you want all your subclasses to share some data. In your example all subclasses will inherit 'i'

[santhosh.R gowda]

Constructors in abstract classes are typically used, when you want all your subclasses to share some data.

Please explain me in detail.....

[Maneesh Godbole]

Which part of my statement did you not understand?

[santhosh.R gowda]

why compiler generates constructer for abstract class what is the need of constructer for abstract class

[Rob Spoor]

Every class needs at least one constructor, for constructor chaining. If a class (abstract or not) does not have a constructor sub classes cannot call it. Therefore, you would not be able to sub class the class at all. In fact, this is exactly what happens if you only provide a private constructor.

[Maneesh Godbole]

I do not think the "decompiled" version posted by the OP is the constructor generated by the compiler. The compiler will generate a default constructor which is no args andempty

[Campbell Ritchie]

Decompilers are hardly a beginners' topic. Moving.

[Seetharaman Venkatasamy]

Maneesh Godbole wrote:I do not think the "decompiled" version posted by the OP is the constructor generated by the compiler.

Yes . i too agree .

[Rob Spoor]

Surprisingly, it is. Apparently the compiler puts all initializations that occur when declaring in source code, into all constructors. For instance:

public class Test
{
    private int x = 10;

    public Test()
    {
        System.out.println("x");
    }

    public Test(int y)
    {
        System.out.println("x");
        System.out.println("y = " + y);
    }
}

// Decompiled by Jad v1.5.8g. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://www.kpdus.com/jad.html
// Decompiler options: packimports(3) 
// Source File Name:   Test.java

import java.io.PrintStream;

public class Test
{

    public Test()
    {
        x = 10;
        System.out.println("x");
    }

    public Test(int i)
    {
        x = 10;
        System.out.println("x");
        System.out.println((new StringBuilder()).append("y = ").append(i).toString());
    }

    private int x;
}

As you can see, the initialization of x to 10 is moved to both constructors.

[Maneesh Godbole]

Interesting.
What do you get if you do not provide any constructors at all? Your existing code has two.
PS. I am not being lazy, but I do not have any decompile tools setup on my home laptop ;)

[Rob Spoor]

It provides a default constructor with the initializer as its body:

// Decompiled by Jad v1.5.8g. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://www.kpdus.com/jad.html
// Decompiler options: packimports(3) 
// Source File Name:   Test.java


public class Test
{

    public Test()
    {
        x = 10;
    }

    private int x;
}

[Maneesh Godbole]

Thanks Rob.
I think its time I dusted off my core java and got down to basics again