jiris mock question

[Shiva Mohan]

    
public class Chapter3{
  static Test t = new Test();
        
        String str;
 
        public static void main(String args[]) 
        {
            Test test = new Test();
            test.method("0");   //line1 
        }
 
        void method(String str) 
        {
            this.str = str;
            System.out.println(str);        
            System.out.println(t.str);        
            System.out.println(this.str);
        }
    }

I have got two errors.

Chapter3.java:74: cannot resolve symbol
symbol : method method (java.lang.String)
location: class Test
test.method("0");
^
Chapter3.java:81: cannot resolve symbol
symbol : variable str
location: class Test
System.out.println(t.str);


1)i have no idea why this line1 is not compiling .
please help me to correct the preceding errors?

2)what is the result of this program.i thought,this would print 0,0,0.Any ideas?

[Chandra Bhatt]

Hi Shiva,

Where is definition for class Test? That's why the error is!


Thanks and Regards,
cmbhatt

[Shiva Mohan]

Chandra, Thanks.one more doubt

why t.str is displaying null insteadof 0 .Can you please give explanation of this?

when i make t as an instance variable,it displayed statckoverflowerror at runtime.what is going on behind this?

[Keith Lynn]

I think you meant to name it Chapter3 and not Test.

[Keith Lynn]

when t is a static reference, it refers to an instance of Chapter3. However, str is an instance variable that is not initialized by a constructor, so it is given its default value.

The reason you get a StackOverflowError when you make t an instance reference is that when a new instance of an object is created, its instance variable initializers are executed before the constructor is executed.

So by having the instance creation statement in the instance variable initializer, you basically have an infinite loop. Eventually the stack will be full.

[Chandra Bhatt]

why t.str is displaying null insteadof 0 .Can you please give explanation of this?

when i make t as an instance variable,it displayed statckoverflowerror at runtime.what is going on behind this?

String str; (member variable of the class Chapter3)
Its default value is null not 0. So when you used t.str obviously it will print null and not 0.

StackOverFlowException:
Are you doing something like this:

    public class TestChap3 { 
 
TestChap3 obj;
{
obj= new TestChap3();
 
}
public static void main(String... args) {
new TestChap3();
 
}
}

The instance initializer executes before the constructor.

Try this code too to have idea...

public class TestChap3 { 
static int i=0; //remove static and try again
 
TestChap3 obj;
{

System.out.println("It is instance init block " + i++);
obj= new TestChap3();

}
public static void main(String... args) {
System.out.println("---------");
new TestChap3();
 

}
}

Thanks and Regards,
cmbhatt