JAVA 基础编程练习题44 程序 44 偶数的素数和

Posted 2022-10-09 denggelin

 

44 【程序 44 偶数的素数和】

题目：一个偶数总能表示为两个素数之和。

 

package cskaoyan;

public class cskaoyan44 
	@org.junit.Test
	public void sum() 
		java.util.Scanner in = new java.util.Scanner(System.in);
		int number = 0;

		do 
			System.out.println("请输入一个偶数:");
			number = in.nextInt();
		 while (number % 2 != 0);

		for (int i = 2; i < number; i++) 
			if (isPrime(i) && isPrime(number - i)) 
				System.out.println("偶数" + number + "可以分解成" + i + "和" + (number - i) + "两个素数的和");
				break;
			
		

		in.close();
	

	private boolean isPrime(int number) 
		boolean flag = true;

		if (number < 2) 
			flag = false;
		 else if (number < 4) 
			flag = true;
		 else if (number % 2 == 0) 
			flag = false;
		 else 
			for (int i = 3; i < Math.sqrt(number) + 1; i++) 
				if (number % i == 0) 
					flag = false;
					break;
				
			
		

		return flag;