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如何在Java中检查数字是否为素数？ 如何生成和打印第一个 N 质数？

已发表: 2020-08-08
如何在Java中检查数字是否为素数？如何在 Java 中生成素数？

什么是质数？

根据定义，大于 1 且只有 1 个本身的除数的 Number 称为Prime number 。 其他数字称为合Composite Number 。

我们来看看：2、3、5、7、11、13是素数。

如果您有以下任何问题，那么您来对地方了。

  • Java中的质数程序
  • 检查数字是否为素数的 Java 程序
  • 用于显示 1 到 200 的素数的 Java 程序
  • 如何在Java中确定质数
  • 在 Java 中生成素数
  • 打印前 500 个素数的总和

前段时间我写了一篇关于如何打印斐波那契数列的文章。 在本教程中，我们将讨论以下几点：

  • Java中确定素数的两种不同方法
  • 在 Java 中生成素数的最佳方法

让我们开始吧：

  1. 创建类 CrunchifyIsPrimeAndGeneratePrime.java
  2. 创建 crunchifyIsPrimeNumber(int) 来检查数字是否为素数？
  3. 创建 crunchifyIsPrimeNumberMethod2(int) 来检查数字是素数还是不使用差异方法
  4. crunchifyGeneratePrimeNumbers(int) 生成介于 2 和提供的数字之间的素数

如何在Java中显示前N个素数？

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package crunchify . com . tutorials ;
 
import java . util . Scanner ;
 
/**
* @author Crunchify.com
* How to Check if Number is Prime or not in Java? How to Generate first N Prime Numbers in Java?
*/
 
public class CrunchifyIsPrimeAndGeneratePrime {
public static void main ( String [ ] args ) {
System . out . println ( crunchifyIsPrimeNumber ( 11 ) ) ;
System . out . println ( crunchifyIsPrimeNumber ( 22 ) ) ;
System . out . println ( crunchifyIsPrimeNumber ( 37 ) ) ;
System . out . println ( crunchifyIsPrimeNumber ( 7 ) ) ;
System . out . println ( "\n" ) ;
System . out . println ( crunchifyIsPrimeNumberMethod2 ( 3 ) ) ;
System . out . println ( crunchifyIsPrimeNumberMethod2 ( 43 ) ) ;
System . out . println ( crunchifyIsPrimeNumberMethod2 ( 23 ) ) ;
System . out . println ( crunchifyIsPrimeNumberMethod2 ( 88 ) ) ;
// Here 120 is an upper limit
crunchifyGeneratePrimeNumbers ( 120 ) ;
System . out . print ( "\n\n------ Let's find out if number is Prime or not ------ \n" +
"Enter Number: " ) ;
Scanner myInput = new Scanner ( System . in ) ;
System . out . println ( crunchifyIsPrimeNumber ( myInput . nextInt ( ) ) ) ;
// Java Program to display first n prime numbers
crunchifyPrintFirstNPrimeNumbers ( 25 ) ;
}
private static String crunchifyIsPrimeNumber ( int crunchifyNumber ) {
System . out . println ( "Prime check started for number: " + crunchifyNumber ) ;
if ( crunchifyNumber == 1 ) {
return "1 is not a Prime number..." ;
}
// Loop starts from 2
for ( int i = 2 ; i < = crunchifyNumber / 2 ; i ++ ) {
if ( crunchifyNumber % i == 0 ) {
return crunchifyNumber + " ==> is not a Prime Number" ;
}
}
return crunchifyNumber + " ==> is a Prime Number" ;
}
// Another way to check if Number is Prime
public static String crunchifyIsPrimeNumberMethod2 ( int crunchifyNumber ) {
System . out . println ( "Prime check started for number: " + crunchifyNumber ) ;
if ( crunchifyNumber == 1 ) {
return "1 is not a Prime number..." ;
}
int limit = ( int ) Math . sqrt ( crunchifyNumber ) ;
for ( int i = 2 ; i < = limit ; i ++ ) {
if ( crunchifyNumber % i == 0 ) {
return crunchifyNumber + " ==> is not a Prime Number" ;
}
}
return crunchifyNumber + " ==> is a Prime Number" ;
}
/*
Generate Prime Numbers
*/
public static void crunchifyGeneratePrimeNumbers ( int crunchifyUpperLimit ) {
System . out . println ( "\n------ Generating all prime number between 2 to " + crunchifyUpperLimit + " ------ " ) ;
for ( int i = 2 ; i < crunchifyUpperLimit ; i ++ ) {
boolean crunchifyIsPrime = true ;
// check to see if the number is prime
for ( int j = 2 ; j < i ; j ++ ) {
if ( i % j == 0 ) {
crunchifyIsPrime = false ;
break ;
}
}
// print the number
if ( crunchifyIsPrime )
System . out . print ( i + " " ) ;
}
}
/*
    Java Program to display first n prime numbers
*/
public static void crunchifyPrintFirstNPrimeNumbers ( int crunchifyFirstNNumber ) {
System . out . println ( "\n------ Generating first " + crunchifyFirstNNumber + " Prime Numbers ------ " ) ;
int crunchifyNumber = 3 ;
int crunchifyCheck = 1 ;
for ( int counter = 2 ; counter < = crunchifyFirstNNumber ; ) {
for ( int incrementer = 2 ; incrementer < = Math . sqrt ( crunchifyNumber ) ; incrementer ++ ) {
if ( crunchifyNumber % incrementer == 0 ) {
crunchifyCheck = 0 ;
break ;
}
}
if ( crunchifyCheck ! = 0 ) {
crunchifyPrint ( crunchifyNumber ) ;
counter ++ ;
}
crunchifyCheck = 1 ;
crunchifyNumber ++ ;
}
}
private static void crunchifyPrint ( int crunchifyNumber ) {
System . out . println ( crunchifyNumber + " " ) ;
}
}
 

在 Eclipse IDE 或 IntelliJ IDEA 中运行 Java 程序，您应该会看到如下所示。

输出：

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/ Library / Java / JavaVirtualMachines / jdk - 15.jdk / Contents / Home / bin / java - javaagent : / Applications / IntelliJ IDEA . app / Contents / lib / idea_rt . jar = 60282 : / Applications / IntelliJ IDEA . app / Contents / bin - Dfile . encoding = UTF - 8
 
Prime check started for number : 11
11 == > is a Prime Number
Prime check started for number : 22
22 == > is not a Prime Number
Prime check started for number : 37
37 == > is a Prime Number
Prime check started for number : 7
7 == > is a Prime Number
 
 
Prime check started for number : 3
3 == > is a Prime Number
Prime check started for number : 43
43 == > is a Prime Number
Prime check started for number : 23
23 == > is a Prime Number
Prime check started for number : 88
88 == > is not a Prime Number
 
------ Generating all prime number between 2 to 120 ------
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 101 103 107 109 113
 
------ Let ' s find out if number is Prime or not ------
Enter Number : 33
Prime check started for number : 33
33 == > is not a Prime Number
 
------ Generating first 25 Prime Numbers ------
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71
73
79
83
89
97
 
Process finished with exit code 0