[英]Java:Counting prime numbers
所以我編寫了這段代碼,我為此感到自豪,因為我很久沒有編碼了。 它做了什么,它要求一個數字,然后打印從1到該數字的所有素數。
import java.util.Scanner;
class PrimeNumberExample {
public static void main(String args[]) {
//get input till which prime number to be printed
System.out.println("Enter the number till which prime number to be printed: ");
int limit = new Scanner(System.in).nextInt();
//printing primer numbers till the limit ( 1 to 100)
System.out.println("Printing prime number from 1 to " + limit);
for(int number = 2; number<=limit; number++){
//print prime numbers only
if(isPrime(number)){
System.out.println(number);
}
}
}
/*
* Prime number is not divisible by any number other than 1 and itself
* @return true if number is prime
*/
public static boolean isPrime(int number){
for(int i=2; i<number; i++){
if(number%i == 0){
return false; //number is divisible so its not prime
}
}
return true; //number is prime now
}
}
但是,我想要它做的是要求一個數字,讓我們拿10,然后打印前10個素數,我試圖看看我是否能找到一種方法,但我不知道如何,因為我有沒用過那么多的java。 我希望你能幫助我。
只計算到目前為止打印了多少個素數。 如果此數字超過10,則停止。 你的循環應該是這樣的:
for(int number = 2; number<=limit; number++){
//print prime numbers only
if(isPrime(number)){
System.out.println(number);
count++;
}
}
整碼:
import java.util.Scanner;
class PrimeNumberExample {
public static void main(String args[]) {
//get input till which prime number to be printed
System.out.println("Enter the amount of prime numbers to be printed: ");
int limit = new Scanner(System.in).nextInt();
int count=0;
//printing primer numbers till the limit ( 1 to 100)
System.out.println("Printing prime number from 1 to " + limit);
for(int number = 2; number<=limit; number++){
//print prime numbers only
if(isPrime(number)){
System.out.println(number);
count++;
}
}
}
/*
* Prime number is not divisible by any number other than 1 and itself
* @return true if number is prime
*/
public static boolean isPrime(int number){
for(int i=2; i<number; i++){
if(number%i == 0){
return false; //number is divisible so its not prime
}
}
return true; //number is prime now
}
}
嘗試這個:
public static void main(String[] args) throws Exception {
// get input till which prime number to be printed
System.out.println("Enter the number till which prime number to be printed: ");
int limit = new Scanner(System.in).nextInt();
// printing primer numbers till the limit ( 1 to 100)
System.out.printf("Printing first %d prime numbers\n", limit);
for (int number = 2; limit > 0; number++) {
if (isPrime(number)) {
System.out.println(number);
limit--;
}
}
}
/*
* Prime number is not divisible by any number other than 1 and itself
*
* @return true if number is prime
*/
public static boolean isPrime(int number) {
for (int i = 2; i < number; i++) {
if (number % i == 0) {
return false; // number is divisible so its not prime
}
}
return true; // number is prime now
}
你也可以嘗試這種方式..
public static void main(String args[]) {
//get input till which prime number to be printed
System.out.println("Enter the number till which prime number to be printed: ");
int limit = new Scanner(System.in).nextInt();
//printing primer numbers till the limit ( 1 to 100)
System.out.println("Printing prime number from 1 to " + limit);
int number = 2;
for(int i = 0; i < limit;){
//print prime numbers only
if(isPrime(number)){
System.out.println(number);
i++;
}
number = number + 1;
}
}
/*
* Prime number is not divisible by any number other than 1 and itself
* @return true if number is prime
*/
public static boolean isPrime(int number){
for(int i=2; i<number; i++){
if(number%i == 0){
return false; //number is divisible so its not prime
}
}
return true; //number is prime now
}
這是一種可以做到需要的方法.....我已經將限制保持為常數10.你也可以從用戶那里閱讀它。
public class PrimeNumberExample {
public static void main(String args[]) {
//get input till which prime number to be printed
System.out.println("Enter the number till which prime number to be printed: ");
int limit = 10;//new Scanner(System.in).nextInt();
//printing primer numbers till the limit ( 1 to 100)
System.out.println("Printing prime number from 1 to " + limit);
int number = 0;
while(true){
if(isPrime(++number)){
System.out.println(number);
if(--limit <= 0)
break;
}
}
}
/*
* Prime number is not divisible by any number other than 1 and itself
* @return true if number is prime
*/
public static boolean isPrime(int number){
for(int i=2; i<(number/2); i++){
if(number%i == 0){
return false; //number is divisible so its not prime
}
}
return true; //number is prime now
}
}
試試這個,它非常容易計算出多少是pritning是最重要的所有!!!
public static void main(String args[]) {
//get input till which prime number to be printed
System.out.println("Enter the number till which prime number to be printed: ");
int limit = new Scanner(System.in).nextInt();
//printing primer numbers till the limit ( 1 to 100)
System.out.println("Printing prime number from 1 to " + limit);
int count = 0;
for(int number = 2; count<limit; number++){
//print prime numbers only
if(isPrime(number)){
count++;
System.out.println(number);
}
}
}
public boolean isPrime(long pNo) {
if(pNo > 9) {
long unitDigit = pNo % 10;
if(unitDigit == 0 || unitDigit%2 == 0 || unitDigit == 5) {
return false;
} else {
for (long i=3; i < pNo/2; i=i+2) {
if(pNo%i == 0) {
return false;
}
}
return true;
}
} else if(pNo < 0) {
return false;
}
else {
return pNo==2 || pNo==3|| pNo==5 || pNo==7;
}
}
public int getPrimeNumberCount(long min, long max) {
int count = 0;
if(min == max) {
System.out.println("Invalid range, min and max are equal");
} else if(max < min || min < 0 || max < 0) {
System.out.println("Invalid range");
} else {
for (long i = min; i <= max; i++) {
if (isPrime(i) && i > 0) {
// System.out.println(i);
count++;
}
}
}
return count;
}
試試這個,它非常容易計算有多少是pritning的數量,所有這些都是使用java 8 !!!
public static void main(String[] args) {
Integer maxVal = 100;
IntStream.iterate(2, i -> ++i)
.parallel()
.filter(i -> !IntStream.rangeClosed(2, i/2).anyMatch(j -> i%j == 0))
.limit(maxVal)
.forEach(System.out::println);
}
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