why is it wrong?

[yanish]

Can anybody explain what's wrong here:
1)

 
public class tester
{
static final int i;
public tester() 
{
i = 0;
}

public tester(int a)
{
i = a;
}

public static void main(String args[])
{
System.out.println( i );
}
}

2)

public class tester
{
java.util.Vector testers;
public tester() throws java.io.IOException 
{
//...
}

public tester(int a) throws java.io.IOException 
{
// ...
}

public void add()
{
testers.add( new tester() { //... });
}


public static void main(String args[])
{
System.out.println( "It works fine" );
}
}

Thank you in advance.

[Deepak M]

in your first case, u have a blank final class variable.
It must be assigned a value in a static initializer.

the second program is a very good code... where'd u get it from ?
The anonymous sub class being created in testers.add( new tester() { }); must throw an IOException in its constructor, coz its super class, i.e tester throws an IOException.
However, anonymous classes cannot have constructors, therefore my conclusion is :
Its not possible to create an anonymous subclass of a class that throws a checked exception in its constructor which takes no parameters.
More generally, it is not possible to create an anonymous subclass that calls any constructor of its superclass which throws a checked exception.

[Ajith Kallambella]

My comments about your second piece of code -
The language doesn't seem to handle anonymous subclasses of classes whose constructors throw exceptions. While one could argue that perhaps this is a language design error, it is in the language by design.
Note that the other alternative, providing an appropriate throws clause for the default constructor automatically, is precluded by JLS 2e 8.8.7, which specifically states that a default constructor has no throws clause.
Can you try compiling your class with JDK1.3?

Ajith

[yanish]

Deepak, Ajith
thank you for your explanations.
Although I can't find a good reason why the Java Specification imposes such restriction on using of anonimous classes, I take it as it's designed.
But especially I like the compiler's error message:
A default constructor cannot be created for this class because the constructor of its superclass throws the exception java.io.IOException. Define the constructor for this class explicitly.
Unfortunately, I can't test it in jdk1.3