Nombre primer a Java: nombre primer és un nombre que és més gran que 1 i dividit per 1 o només per ell mateix. En altres paraules, els nombres primers no es poden dividir per altres nombres que no sigui ell mateix o 1. Per exemple, 2, 3, 5, 7, 11, 13, 17.... són els nombres primers.
Nota: 0 i 1 no són nombres primers. El 2 és l'únic nombre primer parell perquè tots els altres nombres parells es poden dividir per 2.
Vegem el programa de nombres primers en java. En aquest programa java, agafarem una variable numèrica i comprovarem si el nombre és primer o no.
public class PrimeExample{ public static void main(String args[]){ int i,m=0,flag=0; int n=3;//it is the number to be checked m=n/2; if(n==0||n==1){ System.out.println(n+' is not prime number'); }else{ for(i=2;i<=m;i++){ if(n%i="=0){" system.out.println(n+' is not prime number'); flag="1;" break; } if(flag="=0)" { end of else < pre> <span> Test it Now </span> <p>Output:</p> <pre> 3 is prime number </pre> <h2>Prime Number Program using Method in Java</h2> <pre> public class PrimeExample2{ static void checkPrime(int n){ int i,m=0,flag=0; m=n/2; if(n==0||n==1){ System.out.println(n+' is not prime number'); }else{ for(i=2;i<=m;i++){ if(n%i="=0){" system.out.println(n+' is not prime number'); flag="1;" break; } if(flag="=0)" { end of else public static void main(string args[]){ checkprime(1); checkprime(3); checkprime(17); checkprime(20); < pre> <span> Test it Now </span> <p>Output:</p> <pre> 1 is not prime number 3 is prime number 17 is prime number 20 is not prime number </pre> <h2>Prime Number Program in Java (Another way)</h2> <p>You can also use a method where number is not predefined. Here, user has to put the number to check if the number is prime.</p> <pre> import java.util.Scanner; import java.util.Scanner; public class PrimeExample3 { public static void main(String[] args) { Scanner s = new Scanner(System.in); System.out.print('Enter a number : '); int n = s.nextInt(); if (isPrime(n)) { System.out.println(n + ' is a prime number'); } else { System.out.println(n + ' is not a prime number'); } } public static boolean isPrime(int n) { if (n <= 1) { return false; } for (int i="2;" < math.sqrt(n); i++) if (n % 0) true; pre> <p>Output:</p> <strong>Use image PrimeExample1</strong> <h2>Find prime numbers between two numbers</h2> <p>You can also find prime numbers between two specified numbers.</p> <pre> import java.util.Scanner; public class PrimeExample4 { public static void main(String[] args) { Scanner s = new Scanner(System.in); System.out.print('Enter the first number : '); int start = s.nextInt(); System.out.print('Enter the second number : '); int end = s.nextInt(); System.out.println('List of prime numbers between ' + start + ' and ' + end); for (int i = start; i <= end; i++) { if (isprime(i)) system.out.println(i); } public static boolean isprime(int n) (n <="1)" return false; for (int i="2;" % 0) true; pre> <p>Output:</p> <strong>Use image PrimeExample2</strong> </=></pre></=></pre></=m;i++){></pre></=m;i++){> Programa de nombre primer que utilitza el mètode a Java
public class PrimeExample2{ static void checkPrime(int n){ int i,m=0,flag=0; m=n/2; if(n==0||n==1){ System.out.println(n+' is not prime number'); }else{ for(i=2;i<=m;i++){ if(n%i="=0){" system.out.println(n+\' is not prime number\'); flag="1;" break; } if(flag="=0)" { end of else public static void main(string args[]){ checkprime(1); checkprime(3); checkprime(17); checkprime(20); < pre> <span> Test it Now </span> <p>Output:</p> <pre> 1 is not prime number 3 is prime number 17 is prime number 20 is not prime number </pre> <h2>Prime Number Program in Java (Another way)</h2> <p>You can also use a method where number is not predefined. Here, user has to put the number to check if the number is prime.</p> <pre> import java.util.Scanner; import java.util.Scanner; public class PrimeExample3 { public static void main(String[] args) { Scanner s = new Scanner(System.in); System.out.print('Enter a number : '); int n = s.nextInt(); if (isPrime(n)) { System.out.println(n + ' is a prime number'); } else { System.out.println(n + ' is not a prime number'); } } public static boolean isPrime(int n) { if (n <= 1) { return false; } for (int i="2;" < math.sqrt(n); i++) if (n % 0) true; pre> <p>Output:</p> <strong>Use image PrimeExample1</strong> <h2>Find prime numbers between two numbers</h2> <p>You can also find prime numbers between two specified numbers.</p> <pre> import java.util.Scanner; public class PrimeExample4 { public static void main(String[] args) { Scanner s = new Scanner(System.in); System.out.print('Enter the first number : '); int start = s.nextInt(); System.out.print('Enter the second number : '); int end = s.nextInt(); System.out.println('List of prime numbers between ' + start + ' and ' + end); for (int i = start; i <= end; i++) { if (isprime(i)) system.out.println(i); } public static boolean isprime(int n) (n <="1)" return false; for (int i="2;" % 0) true; pre> <p>Output:</p> <strong>Use image PrimeExample2</strong> </=></pre></=></pre></=m;i++){> Programa de nombres primers en Java (una altra manera)
També podeu utilitzar un mètode on el nombre no estigui predefinit. Aquí, l'usuari ha de posar el nombre per comprovar si el nombre és primer.
import java.util.Scanner; import java.util.Scanner; public class PrimeExample3 { public static void main(String[] args) { Scanner s = new Scanner(System.in); System.out.print('Enter a number : '); int n = s.nextInt(); if (isPrime(n)) { System.out.println(n + ' is a prime number'); } else { System.out.println(n + ' is not a prime number'); } } public static boolean isPrime(int n) { if (n <= 1) { return false; } for (int i="2;" < math.sqrt(n); i++) if (n % 0) true; pre> <p>Output:</p> <strong>Use image PrimeExample1</strong> <h2>Find prime numbers between two numbers</h2> <p>You can also find prime numbers between two specified numbers.</p> <pre> import java.util.Scanner; public class PrimeExample4 { public static void main(String[] args) { Scanner s = new Scanner(System.in); System.out.print('Enter the first number : '); int start = s.nextInt(); System.out.print('Enter the second number : '); int end = s.nextInt(); System.out.println('List of prime numbers between ' + start + ' and ' + end); for (int i = start; i <= end; i++) { if (isprime(i)) system.out.println(i); } public static boolean isprime(int n) (n <="1)" return false; for (int i="2;" % 0) true; pre> <p>Output:</p> <strong>Use image PrimeExample2</strong> </=></pre></=>