Java 获取范围内的素数和总素数
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get prime numbers and total prime numbers in range
提问by t_godd
I am a beginner in Java. I am writing this program to show all prime numbers in between the number supplied from the user.
我是 Java 的初学者。我正在编写这个程序来显示用户提供的数字之间的所有质数。
Current output is:
当前输出为：
2, 3, 5, 7, Count: 4
But, i want the output to be like:
但是，我希望输出是这样的：
"The number of prime is: "+count+", and they are: " followed by all the numbers separated by comma
"The number of prime is: "+count+", and they are: " followed by all the numbers separated by comma
package com.example.test;
import java.util.Scanner;
public class PrimeTest {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out
.println("Enter the number till which the prime numbers are to be calculated: ");
int input = scanner.nextInt();
int count = 0;
// loop through the numbers one by one
for (int i = 2; i < input; i++) {
boolean isPrimeNumber = true;
// check to see if the number is prime
for (int j = 2; j < i; j++) {
if (i % j == 0) {
isPrimeNumber = false;
break; // exit the inner for loop
}
}
// print the number if prime
if (isPrimeNumber) {
count++;
System.out.print(i + ", ");
}
}
System.out.println("Count: " + count);
}
}
采纳答案by libik
You have to store the values, for example like this :
您必须存储这些值，例如像这样：
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class PrimeTest {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("Enter the number till which the prime numbers are to be calculated: ");
int input = scanner.nextInt();
List<Integer> primes = new ArrayList<>();
// loop through the numbers one by one
for (int i = 2; i < input; i++) {
boolean isPrimeNumber = true;
// check to see if the number is prime
for (int j = 2; j < i; j++) {
if (i % j == 0) {
isPrimeNumber = false;
break; // exit the inner for loop
}
}
// print the number if prime
if (isPrimeNumber) {
primes.add(i);
}
}
System.out.println("The number of prime is: " + primes.size() + ", and they are: " + primes.toString());
}
}
回答by anirudh
Store the primes in an array and display them at the end, outside the loop.
将素数存储在一个数组中，并在循环外的最后显示它们。
回答by D.R.
Save the generated prime numbers into a List and generate the output in the end. For example:
将生成的素数保存到List中，最后生成输出。例如：
System.out.println("The number of prime is: " + list.size());
foreach(int prime : list)
System.out.print(prime + ", ");
回答by sp00m
Instead of printing a new found prime (System.out.print(i + ", ");), store it in a list (primes.add(i)), and display this list at the end of your program. Your list must be declared outside your forloop (List<Integer> primes = new ArrayList<Integer>();).
不要打印新找到的素数 ( System.out.print(i + ", ");)，而是将其存储在列表 ( primes.add(i)) 中，并在程序结束时显示此列表。您的列表必须在for循环之外声明( List<Integer> primes = new ArrayList<Integer>();)。
回答by t_godd
Thank you every one for helping out.
谢谢大家帮忙。
My final code:
我的最终代码：
package com.example.test;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class PrimeTest {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter the number till which the prime numbers are to be calculated: ");
int input = scanner.nextInt();
scanner.close();
List<Integer> primes = new ArrayList<>();
// loop through the numbers one by one (edit include input in range)
for (int i = 2; i <= input; i++) {
boolean isPrimeNumber = true;
// check to see if the number is prime
for (int j = 2; j < i; j++) {
if (i % j == 0) {
isPrimeNumber = false;
break; // exit the inner for loop
}
}
// print the number if prime
if (isPrimeNumber) {
primes.add(i);
}
}
String s = primes.toString().replace("[", "").replace("]", "");
System.out.println("The number of prime is: " + primes.size() + ", and they are: " + s);
}
}
Output:
输出：
Enter the number till which the prime numbers are to be calculated: 70
The number of prime is: 19, and they are: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67
回答by Sidarth
Get prime numbers and total prime numbers in range
获取范围内的素数和总素数
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class ListPrimeNumbers {
/**
* @param args
* @throws IOException
* @throws NumberFormatException
*/
public static void main(String[] args) throws NumberFormatException, IOException {
int count=0;
int limit;
System.out.println("Enter the Limit:");
InputStreamReader read = new InputStreamReader(System.in);
BufferedReader in = new BufferedReader(read);
limit = Integer.parseInt(in.readLine());
System.out.println("Prime numbers From 1 to " + limit);
//loop from 1 to limit
for(int i=1; i < limit; i++) {
boolean isPrime = true;
//check to see if the number is prime
for(int j=2; j < i ; j++) {
if(i % j == 0) {
isPrime = false;
break;
}
}
// print the number
if(isPrime) {
System.out.print(i + " ");
count++;
}
}
System.out.println("\nTotal Prime Number in given range: "+count);
}
}
Output:
输出：
Enter the Limit:
输入限制：
10
10
Prime numbers From 1 to 10
质数从 1 到 10
1 2 3 5 7
1 2 3 5 7
Total Prime Number in given range: 5
给定范围内的总质数：5
回答by Umit Karahan
I wrote one that lists and count the prime numbers between 1 and any given number without using any boolean. May be you find it interesting.
我写了一个列出和计算 1 和任何给定数字之间的素数，而不使用任何布尔值。可能你觉得很有趣。
public class Main {
public static void main(String[] args) {
int limit = 30; // The program will show prime numbers between 1 and this limit.
System.out.println("Prime numbers between 1 and "+limit+" (except the number 2) :");
System.out.println();
int amount=1; // The amount will give how many prime numbers exist between the interval.
for (int dividend =2; dividend <=limit; dividend++) {
for (int divider=2; divider< dividend; divider++) {
int remaining = dividend % divider;
if (remaining==0){
break;
}
if (divider==dividend-1) {
// If the loop manages to come here without having broken, then the dividend a prime number.
System.out.println(dividend + " IS A PRIME NUMBER.");
amount++;
}
}
}
System.out.println();
System.out.println("There are a total of "+amount+" prime numbers between 1 and "+limit+" including the number 2. ");
}
}
回答by Rahul Sharma
public static void main(String[] args)?
? ? {
? ? ? ? int i,high=10 , low=2,flag ,count=0 ;
? ? ? ??
? ? ? ? while (low<high)
? ? ? ? {
? ? ? ? ? ? flag=0;
? ? ? ? ? ? for (i=2;i<=low/2;i++)
? ? ? ? ? ? {
? ? ? ? ? ? ? ? if (low%i==0)
? ? ? ? ? ? ? ? {
? ? ? ? ? ? ? ? ? ? flag=1;
? ? ? ? ? ? ? ? ? ? break;
? ? ? ? ? ? ? ? }
? ? ? ? ? ? }
? ? ? ? ? ? if (flag==0)
? ? ? ? ? ? { ? ? ??
? ? ? ? ? ? ? ? System.out.println(low);
? ? ? ? ? ? count++;
? ? ? ? }
? ? ? ? ? ? ++low;
? ? ? ? ? ??
? ? ? ? }
? ? ? ??
? ? System.out.println("Total number are: "+count);
}
}
回答by Lakshman Miani
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
public class PrimeNumbersInRange {
public static void main(String[] args) {
int lb = 0, ub = 20;
List<Integer> list = IntStream.rangeClosed(lb,ub)
.filter(PrimeNumbersInRange::isPrime)
.boxed()
.collect(Collectors.toList());
System.out.println(list);
System.out.println(list.size());
}
public static boolean isPrime(int num) {
if (num < 2 || (num > 2 && num % 2 == 0)) {
return false;
}
for (int i = 3; i <= Math.sqrt(num); i++) {
if (num % i == 0)
return false;
}
return true;
}
}
