Programming (Java)

[Witch of Uncertainty]

Sorry if this is completely misplaced, but I'm having a LOT of trouble over a task we got in Java, and I'm wondering whether anyone here oculd help me out?

So basically, my brain is crying over this:
Explain what results you get, and why you get them:

Spoiler for :|:

public static void main(String[] args){
int x = 4;
int y = 5;
int z;
z = A(x,y);
System.out.println("z1=" + z);
z = B(A(x,y),y);
System.out.println("z2=" + z);
z = A(++x,B(x,y));
System.out.println("z3=" + z);
} // end main
private static int A(int a,int b){
int i = b - a;
if (b < 3) i-=b;
return i;
} // end A
private static int B(int c,int d){
int j = c + d;
if (c > 3) j += d;
return j;
} // end B
}// end class

Can anyone help? I would reaaallly appreciate it. This subject is driving me insane!

[Paranoid Android]

What is '++x'
in z=A(++x,B(x,y)); ? I've never seen such an value being passed as an argument. I've only used it as a built in increment method.

My current workstation doens't have java so i just just did this on paper:

-4
1
-4 (if I ignore that ++ argument)

[Renegade334]

Did it first by hand, got confused with all the reused variables then ended up using Eclipse as assistant, but still had to tear everything apart.

Anyway, here's how it's executed:

Spoiler:

First we declare the parameters...

x=4
y=5
z=0


Then off we go:

------

z=A(4,5); <---- Call to function A();
i=5-4;
if (5<3) ...do nothing.
i=1;

display ("1");

------

z=B(1,5); <---- Call to function B(); for how I got the first parameter, see right above ^_^
j = 1 + 5;
if (1>3) ...nope, do nothing.
j=6

display ("6");


------


Third call - break it down to A(++param1, functB());

functB() --V
B(5,5); <----- first parameter has already been incremented (++4 = 5)!!!
j = 5+5;
if (5>3) then, yes, j = 10 + 5;
return 15;


z = A(5, 15);
i = 15-5;
if (10<3) ...nope, do nothing
i=10;

display ("10");


Final output:
z1=1
z2=6
z3=10

And the ++ before the variable indicates a preincrementation.

The difference between ++var and var++ is this:

Spoiler:

Let's write some code:

int var = 4;
System.out.println("1: "+var);
System.out.println("2: "+ ++var);
System.out.println("3: "+var);

System.out.println("---");

var = 4;
System.out.println("1: "+var);
System.out.println("2: "+ var++);
System.out.println("3: "+var);



And let's execute all of that - and read the output:

1: 4
2: 5 <---- var has already been rewritten!
3: 5
---
1: 4
2: 4 <---- not yet rewritten - that will happen AFTER this line of code is executed.
3: 5

See the difference? It all depends on WHEN the incremented value is written back to the variable.

[larethian]

tl;dr. Even though I've not programmed in years, I worked them out mentally, and my answer is the same as Renegade: 1, 6, 10

[Witch of Uncertainty]

Thank you SO much
This is really helpful. I managed to get my head around it (FINALLY) now!

Again, thanks. <3