Java Exercises: Print the number of prime numbers which are less than or equal to a given integer
Java Basic: Exercise-217 with Solution
Write a Java program to print the number of prime numbers which are less than or equal to a given integer.
Input:
n (1 ≤ n ≤ 999,999).
Pictorial Presentation:
Sample Solution-1:
Java Code:
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
System.out.println("Input the number(n):");
Scanner s = new Scanner(System.in);
int c = s.nextInt();
int ans = check(c);
System.out.println("Number of prime numbers which are less than or equal to n.:");
System.out.println(ans);
}
static int check(int c) {
boolean[] prime = new boolean[c+1];
int count = 0;
for(int i = 2; i <= Math.sqrt(c); i++) {
for(int j = i + i; j <= c; j += i) {
prime[j] = true;
}
}
for(int i = 2; i <= c; i++) {
if(!prime[i]) {
count++;
}
}
return count;
}
}
Sample Output:
Input the number(n): 1235 Number of prime numbers which are less than or equal to n.: 202
Flowchart:
Sample Solution-2:
Java Code:
import java.util.Scanner;
public class test {
public static void main(String[] args) {
System.out.println("Input the number(n):");
Scanner s = new Scanner(System.in);
int c = s.nextInt();
int prime_ctr = 0;
for (int i = 2; i <= c; i++) {
if (Check_Prime(i)) {
prime_ctr++;
}
}
System.out.println("Number of prime numbers which are less than or equal to " + c + ": " + prime_ctr);
}
public static boolean Check_Prime(int n) {
for (int divisor = 2; divisor <= n / 2; divisor++) {
if (n % divisor == 0) {
return false;
}
}
return true;
}
}
Sample Output:
Input the number(n): 1235 Number of prime numbers which are less than or equal to 1235: 202
Flowchart:
Java Code Editor:
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Previous: Write a Java program which reads an integer n and find the number of combinations of a,b,c and d (0 ≤ a,b,c,d ≤ 9) where (a + b + c + d) will be equal to n.
Next: Write a Java program to compute the radius and the central coordinate (x, y) of a circle which is constructed by three given points on the plane surface.
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Java: Tips of the Day
How to sort an ArrayList?
Collections.sort(testList); Collections.reverse(testList);
That will do what you want. Remember to import Collections though!
Ref: https://bit.ly/32urdSe
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