int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x = 3

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 2

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 2

{ true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

{ true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

“one”

{ true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

“one”

{

}

true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

“one”

{

}

true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

“one”

{

}

true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

“one”

{

}

true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

“three” “one”

{

}

true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

“three” “one”

{

}

true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

“three” “one”

{

}

true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

“three” “one”

{

}

true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

“three” “one”

“four”

{

}

true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

“three” “one”

“four”

{

}

true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

“three” “one”

“four”

{

}The end.

true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

x > 1

x = 3

x > 3

x > 2

“three” “one”

“four”

{

}The end. The end. Nothing gets printed.

true

true

true

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

Old problem

int x = 3;

if (x > 1) {

if (x > 2)

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

New problem

int x = 3;

if (x > 1)

if (x > 2) {

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

Old problem

int x = 3;

if (x > 1) {

if (x > 2)

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

New problem

int x = 3;

if (x > 1) {

if (x > 2)

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

New problem

else w/out if

Does not compile!

int x = 3;

if (x > 1) {

if (x > 2)

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

New problem

else w/out if

Does not compile!

The only solution, then, is to carefully draw the flowchart!

int x = 3;

if (x > 1) {

if (x > 2)

if (x > 3)

System.out.println("one");

} else System.out.println("three");

else System.out.println("four");

New problem

else w/out if

Does not compile!

The only solution, then, is to carefully draw the flowchart!

There really isn’t any reliable, uniform shortcut alternative to that.

Let’s take a look at the lab assignment.

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

So you can give the user the change (if any).

initialize the amount the user needs to pay

while (the amount due is more than zero) {

prompt the user for input (a line)

get the line and prepare to take it apart

while (there are still tokens available) {

get next token (call it token)

interpret it, and update amount

}

// if you get here you’re done with the line

// but the amount due can still be positive

}

// if you get here the amount due is zero or less

Now let’s talk about the homework problems…

1. The Wizard Problem

You are to define a class of objects that (once created) can take simple

(math) questions. The following three requirements are to be met:

a) wizards know how to calculate the greatest common divisor of two integers

b) a wizard can list the prime factors of any positive integer

c) a wizard can tell you if an integer is prime or not