Java Goldbach's Conjecture

Hello everyone, I'm Ziph!

At first I do not know, I would like to do, this is the Goldbach conjecture it? Later, a Wikipedia learned that it is one of the world's three major modern mathematical problems. This is a more powerful Ha, instantly feeling the bald head! Few know how to feel good, but now you except to refuel the effort have no choice! Aha!

Title :
Enter a even number greater than 6, the output of the even request which can be decomposed into two prime numbers and. Such as: 10 = 3 + 7 + 5 = 712

Requirements: Two groups of collaboration. A person responsible for an integer n and split into two integers, another person is responsible for writing a function, it determines a certain integer is a prime number.

Edition functions

//质数的校验
//普通的方法判断是否质数
//质数是指在大于1的自然数中，除了1和它本身以外不再有其他因数的自然数。
	public static boolean isPrime(int i) {
        for (int j = 2; j < i - 1; j++) {
            if (i % j == 0) {
                return false;
            }
        }
        return true;
    }

Optimized version function

//质数的校验
//开始我也只是一知半解，后来明白的所以也就写了下来，记录一下
//在哥德巴赫猜想中，一个数的因子是成对出现的，比如：100 = 2 * 50、100 = 4 * 25等
//所以，一个数a，它的的因子，一个肯定是<=根号下a的，另一个肯定是>=根号下a的
//因为我们两个数，一个是i，一个是j=a-i
//所以我们只要判断他们符合条件即可
public static boolean isPrime(int i){
		double m = Math.sqrt(i);
		for(int j = 3 ; j <= m ; j += 2){
			if (i % j == 0) {
				return false;
			}
		}
		return true;
	}

The full version of the code

import java.util.Scanner;

/** 
* @author Ziph
* @date 2020年2月26日
* @Email [email protected]
*/
public class Goldbach {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		System.out.print("请输入一个大于6的偶数：");
		int a = sc.nextInt();
		
		//输入校验
		while (a < 6 || a % 2 != 0) {
			System.out.println("输入错误！");
			System.exit(0);
		}
		
		//将输入的值拆分成两个数，i代表第一个数，j代表第二个数
		for (int i = 3; i < a / 2; i += 2) {
			int j = a - i;
			//判断两个数均为质数
			if (isPrime(i) && isPrime(j)) {
				//打印输出结果
				System.out.println(a + " = " + i + " + " + j);
			}
		}
	}

	//质数的校验
	public static boolean isPrime(int i) {
        for (int j = 2; j < i - 1; j++) {
            if (i % j == 0) {
                return false;
            }
        }
        return true;
    }
}