Q:

generate all prime number less than n java (fastest method)

/**
Author: Jeffrey Huang
As far as I know this is almost the fastest method in java
for generating prime numbers less than n.
A way to make it faster would be to implement Math.sqrt(i)

I don't know if you could implement sieve of eratosthenes in
this, but if you could, then it would be even faster.

If you have any improvements please email me at
jeffreyhuang9[email protected]
*/

import java.util.*;

public class Primecounter {

public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
//int i =0;
int num =0;
//Empty String
boolean isPrime = true;
System.out.print("Enter the value of n: ");
System.out.println();
int n = scanner.nextInt();

for (int i = 2; i < n; i++) {
isPrime = true;
for (int j = 2; j <= i/2; j++) {
if (i%j == 0) {
isPrime = false;
}
}
if (isPrime)
System.out.print(" " + i);
}

}
}
2

/**
Author: Jeffrey Huang
As far as I know this is almost the fastest method in java
for generating prime numbers less than n.
A way to make it faster would be to implement Math.sqrt(i)

I don't know if you could implement sieve of eratosthenes in
this, but if you could, then it would be even faster.

If you have any improvements please email me at
[email protected]
*/

import java.util.*;

public class Primecounter {

public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
//int i =0;
int num =0;
//Empty String
boolean isPrime = true;
System.out.print("Enter the value of n: ");
System.out.println();
int n = scanner.nextInt();

for (int i = 2; i < n; i++) {
isPrime = true;
for (int j = 2; j <= i/2; j++) {
if (i%j == 0) {
isPrime = false;
}
}
if (isPrime)
System.out.print(" " + i);
}

}
}
0