jtips ques

[gaurav nayyar]

class Servlets {
Servlets(String s) {
System.out.println(s);
}
void writeLn(String s) {
System.out.println(s);
}
}
class Form {
static Servlets s1 = new Servlets("J as in Jam");
Form() {
s2.writeLn("V as in Victor");
}
void writeLn(String s) {
System.out.println(s);
}
static Servlets s2 = new Servlets("A as in Apple");
}
class JSP {
Servlets s3 = new Servlets("S as in Sam");
static Servlets s4 = new Servlets("A as in Apple");
JSP() {
s4.writeLn("P as in Pollard");
}
void writeLn(String s) {
System.out.println(s);
}
static Servlets s5 = new Servlets("J as in John");
}
public class Q52 {
public static void main(String[] args) {
System.out.println("Trimming J from JSP in main()...");
new JSP();
f.writeLn("A Simple Example of static Initialization !");
j.writeLn("A Simple Example of Instance Initialization !");
}
static Form f = new Form();
static JSP j = new JSP();
}
What is the Output?
1.Prints
Trimming J from JSP in main()�
S as in Sam
P as in Pollard
A Simple Example of static Initialization !
A Simple Example of Instance Initialization !
J as in Jam
A as in Apple
V as in Victor
A as in Apple
J as in John
S as in Sam
P as in Pollard
2.Prints
J as in Jam
A as in Apple
V as in Victor
A as in Apple
J as in John
S as in Sam
P as in Pollard
Trimming J from JSP in main()�
S as in Sam
P as in Pollard
A Simple Example of static Initialization !
A Simple Example of Instance Initialization !

3.Prints
Trimming J from JSP in main()�
S as in Sam
A as in Apple
J as in John
P as in Pollard
A Simple Example of static Initialization !
A Simple Example of Instance Initialization !
J as in Jam
A as in Apple
V as in Victor
S as in Sam
A as in Apple
J as in John
P as in Pollard
4.Prints
J as in Jam
A as in Apple
V as in Victor
A as in Apple
J as in John
S as in Sam
P as in Pollard
Trimming J from JSP in main()�
A as in Apple
J as in John
S as in Sam
P as in Pollard
A Simple Example of static Initialization !
A Simple Example of Instance Initialization !
the answer is 2 but i cant get it

[Manfred Leonhardt]

Hi Gaurav,
Lets take it one part at a time.
We start things off in the Q52 class. Static variables are initialized during class load. Therefore we start with the first line:
1. static Form f = new Form();
this causes the Form class to be loaded. The Form class has its own static variables that get initialized now:
2. static Servlets s1 = new Servlets("J as in Jam");
This line causes the Servlets class to be loaded and its constructor called. The Servlets class constructor has a print in it, therefore we get
J as in Jam
as the first output. The second static variable inside Form:
3. static Servlets s2 = new Servlets("A as in Apple");
causes the Servlets constructor to print out
A as in Apple
We are now done with the static variables inside the Form class (and no non-static ones exist) so we can go ahead and run the Form constructor to complete the line numbered 1 above. It also has a print inside of it so we get
V as in Victor
Now we are done with the first static variable inside Q52 we can move to the next one
4. static JSP j = new JSP();
This causes the JVM to load the JSP class. It has its' own static variables that must be initialized.
5. static Servlets s4 = new Servlets("A as in Apple");
This will run the Servlets constructor since it has already been loaded. The constructor will print
A as in Apple
The second static initialization can now be executed.
6. static Servlets s5 = new Servlets("J as in John");
Once again the constructor prints out:
J as in John
Now we have completed the static variable initialization we can go ahead and perform the non-static one:
7. Servlets s3 = new Servlets("S as in Sam");
This once again causes the print of
S as in Sam
We can now run the JSP constructor to complete the line numbered 4 above. The JSP constructor has a print that will output
P as in Pollard
We have now completed all the Q52 variable initializations so we can now go ahead and execute the main method. It starts out with a print
Trimming J from JSP in main()...
Moving to the next line inside main
8. new JSP();
This line now will make a new JSP object so the non-static variables need to be initialized first before we run the constructor. The line
9. Servlets s3 = new Servlets("S as in Sam");
will be executed and will print out the following line
S as in Sam
Now we can run the JSP constructor to complete the line numbered 8 above. It will print out:
P as in Pollard
We are now ready to run the fourth line inside the Q52 main method:
10. f.writeLn("A Simple Example of static Initialization !");
this will run the writeLn method for the Form object. It will print out
A Simple Example of static Initialization !
The next line to be executed will be
11. j.writeLn("A Simple Example of Instance Initialization !");
this will run the writeLn method for the JSP object. It will print out
A Simple Example of Instance Initialization !
This completes the execution of Q52 main method.
Regards,
Manfred.

[gaurav nayyar]

Hi Manfred ,
thanks for the explanation
Gaurav