Loops

Just like in Alice or AppInventor it is often useful to use loops to repeat code statements. Even if something is being repeated just 2x, it is useful to use loops because:

• Makes coding faster
• Better readability
• If you make a change to your code in the loop, you change it in one place.

The two main types of loops are

• while
• for

while loops

while (condition is true)

{
	do this
}

for example

int i=0;

while (i<10)
{
	System.out.println(i);
	i++;
}

for loops

are in the format: for (this counter variable staring here, while this condition met, do this to the counter)

for (int i=0; i<10; i++)
{
	System.out.println("We are at" + i);
}

this would repeat the inside 10 times (while i was 0 through 9)

Exiting (not used all that often, just reference)

To exit the current loop, you use the statement:

break;

Lets create these methods: HERE IS STARTER CODE

• public void printSandyFor() that will print I hate Sandy 50 times. Do this with a for loop
• public void printSandyWhile() that will print illegal character 50 times. Do this with a while loop
• public void printNumbers(int max) that will print the numbers from 1 to max on one line like 1,2,3,4,5,6,7,....,150 [if max was 150] (note: no comma at end)
• public void printOdds(int start, int end) that will print the odd numbers from start to end; assume start is odd. (note you wont use scanner.)
• public void insultUser() that will insult the user and then say do you want another insult (y or n) if they say y it will repeat, if they so n it will end. [advanced - have it choose from 1 of 5 insults randomly]
• extra credit:
  1. public void puzzleNumber() that will solve this puzzle: how many numbers between 1-1000 have a product of their digits greater than 50 like 439 is 4*3*9 which is greater than 50. Print out all the numbers and say how many there were.
  2. Print out the first 30 prime numbers [you will need to know % (modulo operator) which gives the remainder, like 5%2 is 1 or 40%8=0 or 13%5 =3 or 24%5=4]
  3. Find the smallest positive integer that if it is divided by 7, 9, and 11 the remainders are 1, 2, and 3 respectively.
  4. Find all the two-digit prime numbers with the product of its digits equal to a
     prime number.

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