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Prime Number From 1 to 100 Program in Java

Prime Number From 1 to 100 Program in Java

What is a Prime Number?

A prime number is a number that is only divisible by 1 or itself. For example, 11 is only divisible by 1 or itself. Other Prime numbers 2, 3, 5, 7, 11, 13, 17….

Note: 0 and 1 are not prime numbers. 2 is the only even prime number.

How to display prime numbers between 1 to 100 using Java Code

Program Logic:

  • The main method contains a loop to check prime numbers one by one.
  • The main method calls the method CheckPrime to determine whether a number is prime
  • We need to divide an input number, say 17 from values 2 to 17 and check the remainder. If the remainder is 0 number is not prime.
  • No number is divisible by more than half of itself. So, we need to loop through just numberToCheck/2. If the input is 17, half is 8.5, and the loop will iterate through values 2 to 8
  • If numberToCheck is entirely divisible by another number, we return false, and loop is broken.
  • If numberToCheckis prime, we return true.
  • In the main method, check isPrime is TRUE and add to primeNumbersFound String
  • Lastly, print the results
  • public class primeNumbersFoundber {
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  • public static void main(String[] args) {
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  • int i;
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  • int num = 0;
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  • int maxCheck = 100; // maxCheck limit till which you want to find prime numbers
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  • boolean isPrime = true;
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  • //Empty String
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  • String primeNumbersFound = “”;
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  • //Start loop 1 to maxCheck
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  • for (i = 1; i <= maxCheck; i++) {
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  • isPrime = CheckPrime(i);
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  • if (isPrime) {
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  • primeNumbersFound = primeNumbersFound + i + ” “;
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  • }
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  • }
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  • System.out.println(“Prime numbers from 1 to “ + maxCheck + ” are:”);
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  • // Print prime numbers from 1 to maxCheck
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  • System.out.println(primeNumbersFound);
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  • }
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  • public static boolean CheckPrime(int numberToCheck) {
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  • int remainder;
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  • for (int i = 2; i <= numberToCheck / 2; i++) {
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  • remainder = numberToCheck % i;
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  • //if remainder is 0 than numberToCheckber is not prime and break loop. Elese continue loop
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  • if (remainder == 0) {
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  • return false;
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  • }
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  • }
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  • return true;
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  • }
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  • }

Output:

Prime numbers from 1 to 100 are:
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

Check our program to Find Prime Numbers from Any Input Number