Write a program to find first n prime numbers in Java
In this tutorial, we will discuss the concept of an Example program – write a program to find first n prime numbers in Java.
In this post, we are going to learn how to write a program to find the first n prime number using for, while, and do-while loops in Java programming language:
The number that can be divided by 1 and itself only. it is called the prime number
for Example 2,3,5,7,11,13,….
To understand this example program, you should have previous knowledge of the following Java topics
do-while loop in Java language
Example program to print first n prime numbers
Print the first n prime number using the for loop
In this program, we will print the first “n” prime numbers, using for loop. first, the user is asked to enter a number randomly for n, and then the program prints the prime numbers 1 to n.
Program 1
//print the prime number in given range(0 - n)
import java.util.*;
public class PrimeNum_firstN1{
public static void main(String args[]){
Scanner sc=new Scanner(System.in);
//scanner class for input
int num=1,y=3,count,j;
//variable declaration and initialization
System.out.println("Please Enter the number for range(0 - n): ");
int n=sc.nextInt();
if(n>=1){
System.out.println("The first "+n+" prime numbers are: " );
System.out.println(2);
}
for(count=2; count<=n;){
for(j=2; j<=Math.sqrt(y); j++){
if(y%j==0){
num=0;
break;
}
}
if(num!=0){
System.out.println(y);
count++;
}
num=1;
y++;
}
}
}
When the above code is executed, it produces the following result
Please Enter the number for range(0 - n): 10 The first 10 prime numbers are: 2 3 5 7 11 13 17 19 23 29
Print the first n prime number using the while loop
In this program, we will print the first “n” prime numbers, using a while loop. first, the user is asked to enter a number randomly for n, and then the program prints the prime numbers 1 to n.
Program 2
//print first n prime numbers using while
import java.util.*;
public class Prime_firstNwhile{
public static void main(String args[]){
Scanner sc=new Scanner(System.in);
//scanner class for input
int n,num=1,y=3,count,j;
System.out.println("Please Enter the number for print prime: ");
n=sc.nextInt();
if(n>=1){
System.out.println("First "+n+" prime numbers are: " );
System.out.println(2);
}
count=2;
while(count<=n){
j=2;
while(j<=Math.sqrt(y)){
if(y%j==0){
num=0;
break;
}
j++;
}
if(num!=0){
System.out.println(y);
count++;
}
num=1;
y++;
}
}
}
When the above code is executed, it produces the following result
Please Enter the number for range(0 - n): 5 The first 5 prime numbers are: 2 3 5 7 11
Print the first n prime number using the do-while loop
In this program, we will print the first “n” prime numbers, using a do-while loop. first, the user is asked to enter a number randomly for n, and then the program prints the prime numbers 1 to n.
Program 2
//Print first n prime numbers using do-while
import java.util.*;
public class Prime_FirstNDowhile2{
public static void main(String args[]){
Scanner sc=new Scanner(System.in);
//scanner class for input
int n,num=1,y=3,count,j;
System.out.println("Please Enter the number for print prime: ");
n=sc.nextInt();
if(n>=1){
System.out.println("The First "+n+" prime numbers are: " );
//display first n priume number
System.out.println(2);
}
count=2;
do{//outer do-while
j=2;
do{//inner do-while
if(y%j==0){
num=0;
break;
}
j++;
}while(j<=Math.sqrt(y));
if(num!=0){
System.out.println(y);
count++;
}
num=1;
y++;
}while(count<=n);
}
}
When the above code is executed, it produces the following result
Please Enter the number for print prime: 7 The first 5 prime numbers are: 2 3 5 7 11 13 17
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