# Head First Java exercise problem

Louis Merz

Greenhorn

Posts: 2

posted 5 years ago

Hello everyone,

Lately I've been trying to learn Java with the Head First Java book. It seems like a good book so far except it's frustrating because the book doesn't explain how the code works in the exercises at the end of the chapters. They give the solutions to the exercises but no explanation.

Any help understanding how this code gets the following output would be great, thanks!

Program Output: 00 11 21 32 42

Lately I've been trying to learn Java with the Head First Java book. It seems like a good book so far except it's frustrating because the book doesn't explain how the code works in the exercises at the end of the chapters. They give the solutions to the exercises but no explanation.

Any help understanding how this code gets the following output would be great, thanks!

Program Output: 00 11 21 32 42

Ian Paul Budiman

Greenhorn

Posts: 7

posted 5 years ago

- 1

Hi Louise,

I am a newbie also, but the logic solution for that particular is:

You will print out value X, Value Y from X=0, X=1, X=2, X=3, X=4

Which the format would be: "System.out.print(x + "" + y +" "); "

As you know the given parameter is, x = x + 1 and y = x - y

So, it will give you result:

when x=0

0,

when x=1

1,

when x=2

2,

when x=3

3,

when x=4

4,

Which the

Hope it helps.

I am a newbie also, but the logic solution for that particular is:

You will print out value X, Value Y from X=0, X=1, X=2, X=3, X=4

Which the format would be: "System.out.print(x + "" + y +" "); "

As you know the given parameter is, x = x + 1 and y = x - y

So, it will give you result:

when x=0

0,

**0**(0-0)when x=1

1,

**1**(1-**0**)when x=2

2,

**1**(2-**1**)when x=3

3,

**2**(3-**1**)when x=4

4,

**2**(4-**2**)Which the

**bold**part is "Y"Hope it helps.

Louis Merz

Greenhorn

Posts: 2

posted 5 years ago

Try taking it out, and see what you get!!!

System.out.print(x + y + " ");

Louis Merz wrote:Also I'm not sure what the "" in the "System.out.print(x + "" + y + " "); " means. Does it simply mean the program will print two numbers at a time?

Try taking it out, and see what you get!!!

System.out.print(x + y + " ");

There are only two hard things in computer science: cache invalidation, naming things, and off-by-one errors

posted 5 years ago

Thank you so much Anayonkar - it makes sense now.

The second part of this question has this piece of code in place of (y = x - y)

code:

x = x + 1

y = y + x

with outcome expected to be: 11 34 59

Am I correct in saying that, to work out the y-axis, you'd first need to add +1 to the value of x, before you can plug in that value into (y = y + x) to get your corresponding y-axis value?

Rgds

Ricci

Anayonkar Shivalkar wrote:

New value of y = current value of x - current value of y.

Thank you so much Anayonkar - it makes sense now.

The second part of this question has this piece of code in place of (y = x - y)

code:

x = x + 1

y = y + x

with outcome expected to be: 11 34 59

Am I correct in saying that, to work out the y-axis, you'd first need to add +1 to the value of x, before you can plug in that value into (y = y + x) to get your corresponding y-axis value?

Rgds

Ricci

Campbell Ritchie

Marshal

Posts: 52519

119

posted 5 years ago

Welcome to the Ranch

I don’t think those values are axes, but simply

I don’t think those values are axes, but simply

*x*and*y*. I think the bit about "" previously might be a misprint and should have read " ", which means you get 1 1 instead of 11. I don’t have my copy of the book to hand at present.