Java Tricky Program 1 - Java Compiler Optimization

A program where output seems simple but it's not because of java compiler optimization of the byte code.

From Java Specs:
If a primitive type or a string is defined as a constant and the value is known at compile time, the compiler replaces the constant name everywhere in the code with its value. This is called a compile-time constant. If the value of the constant in the outside world changes (for example, if it is legislated that pi actually should be 3.975), you will need to recompile any classes that use this constant to get the current value.

[omkarjoshi]

thanks !! indeed tricky questions set.... Please keep posting more of these.

[satyavarapujagadeeswararao]

Hi, Sir the information which is you are providing is very useful. I have tried the same program with small change like "assigned the final variable in a static block " in this scenario the static block is executing first. So can you please explain the scenario once.

[georgegeorgiadis]

I think this happens because there is no object instantiation with the keyword new (that is the reason static code is never called). It is very interesting to add a constructor in class T that simply prints a message and in the main program to instantiate 2 objects. The static code will be called once.

[shubhamchaudhary]

sir what is this static block ...is it a function, if it is why it doesnt have some name?

[virendrayadav]

What if Class Test extends Class T? what will be the output

[tamalsaha]

you cannot initialize static block in inner class unless it is static inner class

[johnkanathon]

Hi Pankaj

Which tool you are using for this screen cast?

[SandeepKumar-jqet]

What if x in initialised as default Int?

[sandeepmaurya]

thank you sir for such a trick program

[MrRobot-oxox]

This program will compile only when inner class is static.

[debadattabiswal]

This program will compile only when inner class is static. :)

[lkhore]

class Test {
public static void main(String[] args) {
T t = new T();
System.out.println(t.x);
}
}

class T {
public final int x = 100;

static {
System.out.printf("T loaded");
}
}


in the above class x is also final but it is printed T loaded data.