Finding Prime Numbers

Write a function like so:

public static boolean isPrime( int n )

The function should return the value true if n is a prime and false otherwise.

Remember that a number is prime if is isn't evenly divisible by anything except for 1 and itself. You can figure this out by using a for loop inside the function.

Make the for loop run through all the numbers from 2 up to n. Inside the loop, use an if statement that determines if n is evenly divisible by your loop control variable.

If you find any number which divides it evenly, you can go ahead and return false from the function without finishing the loop.

If the loop finishes and doesn't find any numbers which divide it, then return true from the function.

After you finish writing the function write a main() that contains another for loop. Have it print out all the numbers from 2 to 20, and mark each prime number with a "<".

2 <
3 <
4
5 <
6
7 <
8
9
10
11 <
12
13 <
14
15
16
17 <
18
19 <
20

If you prefer, you may print out only the prime numbers up to 100 or so, like this:

2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71
73
79
83
89
97


©2013 Graham Mitchell

This assignment is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Creative Commons License