第二章第十一题（人口统计）(Population projection)

2.11（人口统计）重写编程练习题1.11，提示用户输入年数，然后显示这个年数之后的人口值。将编程练习题1.11中的提示用于这个程序。

下面是一个运行示例：
Enter the number of years:5
The population in 5 years is 325932969

2.11(Population projection) Rewrite Programming Exercise 1.11 to prompt the user to enter the number of years and display the population after the number of years. Use the hint in Programming Exercise 1.11 for this program.

Here is a sample run of the program:
Enter the number of years:5
The population in 5 years is 325932969

下面是参考答案代码:

import java.util.*;

public class PopulationProjectionQuestion11 {
	public static void main(String[] args) {
		final double BORN_NUMBER = 1.0 / 7; 		// Births per second
		final double DEAD_NUMBER = 1.0 / 13;		// Deaths per second
		final double IMMIGRANT_NUMBER = 1.0 / 45;	// Number of immigrants per second
		final int SECONDS_IN_A_YEAR = 365 * 24 * 60 * 60; // Seconds in a year
		int year;
		
		System.out.print("Enter the number of years:");
		Scanner YearInput = new Scanner(System.in);
		year = YearInput.nextInt();
		
		
		int SecondsInTheYear = SECONDS_IN_A_YEAR * year;
		
		int PopulationNumberNow = 312_032_486;
		int YearPopulation =(int)(PopulationNumberNow + SecondsInTheYear * BORN_NUMBER
										- SecondsInTheYear * DEAD_NUMBER
										+ SecondsInTheYear * IMMIGRANT_NUMBER);
		
		System.out.println("The population in " + year + " years is "+ YearPopulation);
	}
}

运行效果：

注：编写程序要养成良好习惯
如：1.文件名要用英文，具体一点
2.注释要英文
3.变量命名要具体，不要抽象（如:a,b,c等等），形式要驼峰化
4.整体书写风格要统一（不要这里是驼峰，那里是下划线，这里的逻辑段落空三行，那里相同的逻辑段落空5行等等）

来源：CSDN

作者：xjlovewjh

链接：https://blog.csdn.net/xjlovewjh/article/details/104122091