《Java技术》第一次作业

（一）学习总结

1.在java中通过Scanner类完成控制台的输入，查阅JDK帮助文档，Scanner类实现基本数据输入的方法是什么？不能只用文字描述，一定要写代码，通过具体实例加以说明。

import java.util.*;

public class ABC {
	public static void main(String[] args) {
            int a;
            Scanner input = new Scanner(System.in);
            a = input.nextInt();
            System.out.println(a);
}

这就是输入一个int型的数，如果想要输入一个double型的数就把next后面的int改成double。如果要输入一个字符串，next后面就不用写东西。

2.Random类和Math类的random()方法都能产生随机数，这两种方式有什么区别，各有什么特点呢？查阅JDK帮助文档，并举例加以说明。

Math类：int x=(int)(Math.random()*x+y); 就是产生一个x-y之间的数。
Random类：
Random rand = new Random();
int x=rand.nextInt(x)+y;
就是产生一个x-y之间的数。

3.运行下列程序，结果是什么？查阅资料，分析为什么。

输出结果是不等于0.3，因为在计算double类型数据时会产生误差。
比较两个double类型的数据相等时，看二者相减是否无限趋近于0.

public class ABC {
    public static void main(String args[]) { 
        double a = 0.1;
        double b = 0.1;
        double c = 0.1;
        if((a + b + c)-0.3<1e-6){
            System.out.println("等于0.3");
        }else {
            System.out.println("不等于0.3");
        }
    }     
}

（二）实验总结

实验内容：

1.看商品猜价格

import java.util.*;

public class ABC {
	public static void main(String[] args) {
		int x = 0, a = 0, i = 0, j = 0, k = 0, n = 0;
		String t;
		Scanner input = new Scanner(System.in);
		ww: while (true) {
			x = (int) (Math.random() * 100);
			k = 100;
			for (i = 5; i > 0; i--) {
				System.out.println("请输入商品价格，还有" + i + "次机会");
				a = input.nextInt();
				if (a == x) {
					System.out.println("猜对了");
					j += k;
					break;
				}
				if (a > x) {
					System.out.println("猜大了");
					k -= 20;
				}
				if (a < x) {
					System.out.println("猜小了");
					k -= 20;
				}
				if (i == 1) {
					System.out.println("正确答案是" + x);
				}
			}
			n++;
			System.out.println("是否进行下一轮？输入yes进行下一轮，输入no退出游戏");
			while (true) {
				t = input.next();
				if (t.equals("yes")) {
					System.out.println("进行下一轮");
					break;
				} else if (t.equals("no")) {
					System.out.println("退出游戏");
					break ww;
				} else {
					System.out.println("输入错误，请重新输入");
				}
			}
		}
		System.out.println("一共猜了" + n + "次，总得分为" + j);
	}
}

2.万年历

import java.util.*;

public class ABC {

	public static void main(String[] args) {
		int year, year1, month, sum, sum1, sum2, i, n, zong = 0, h = 0;
		Scanner input = new Scanner(System.in);
		while (true) {
			System.out.println("请输入年份");
			year = input.nextInt();
			System.out.println("请输入月份");
			month = input.nextInt();
			if (year < 1900 || month < 1 || month > 12) {
				System.out.println("输入错误，请重新输入");
			} else {
				break;
			}
		}
		sum1 = 0;
		sum2 = 0;
		year1 = year;
		for (year1 = year1 - 1; year1 >= 1900; year1--) {
			if (year1 % 4 == 0 && year1 % 100 != 0 || year1 % 400 == 0) {
				sum1 = sum1 + 366;
			} else {
				sum1 = sum1 + 365;
			}
		}

		for (i = 1; i < month; i++) {
			if (i == 1 || i == 3 || i == 5 || i == 7 || i == 8 || i == 10 || i == 12) {
				sum2 = sum2 + 31;
			} else if (i == 4 || i == 6 || i == 9 || i == 11) {
				sum2 = sum2 + 30;
			} else if (i == 2) {
				if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
					sum2 = sum2 + 29;
				} else {
					sum2 = sum2 + 28;
				}
			}
		}
		sum = sum1 + sum2;
		System.out.println("星期日	星期一	星期二	星期三	星期四	星期五	星期六");
		switch (sum % 7) {
		case 0:
			System.out.print("	");
			h = 2;
			break;
		case 1:
			System.out.print("		");
			h = 3;
			break;
		case 2:
			System.out.print("			");
			h = 4;
			break;
		case 3:
			System.out.print("				");
			h = 5;
			break;
		case 4:
			System.out.print("					");
			h = 6;
			break;
		case 5:
			System.out.print("						");
			h = 7;
			break;
		case 6:
			h = 1;
			break;
		}
		if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12) {
			zong = 31;
		} else if (month == 4 || month == 6 || month == 9 || month == 11) {
			zong = 30;
		} else if (month == 2) {
			if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
				zong = 29;
			}

			else {
				zong = 28;
			}
		}

		for (n = 1; n <= zong; n++, h++) {
			System.out.print(n + "	");
			if (h % 7 == 0) {
				System.out.println(" ");
			}
		}

	}
}

3.评分系统

import java.util.*;

public class ABC {

	public static void main(String[] args) {
		int a[][] = new int[5][10];
		int b[][] = new int[5][8];
		int i = 0, j = 0, k = 0, t = 0;
		double n, x, y;
		double c[] = new double[5];
		int d[] = new int[5];
		Scanner input = new Scanner(System.in);
		for (i = 0; i <= 4; i++) {
			for (j = 0; j <= 9; j++) {
				System.out.println("请第" + (j + 1) + "位评委给第" + (i + 1) + "号选手打分");
				a[i][j] = input.nextInt();
			}
		}
		for (i = 0; i <= 4; i++) {
			for (j = 0; j <= 9; j++) {
				for (k = 0; k <= 8; k++) {
					if (a[i][k] > a[i][k + 1]) {
						t = a[i][k];
						a[i][k] = a[i][k + 1];
						a[i][k + 1] = t;
					}
				}
			}
		}
		for (i = 0; i <= 4; i++) {
			for (j = 0; j <= 7; j++) {
				b[i][j] = a[i][j + 1];
			}
		}
		for (i = 0; i <= 4; i++) {
			n = 0;
			x = 0;
			for (j = 0; j <= 7; j++) {
				n++;
				x += b[i][j];
			}
			c[i] = x / n;
			d[i] = i + 1;
		}
		for (i = 0; i <= 4; i++) {
			for (k = 0; k <= 3; k++) {
				if (c[k] < c[k + 1]) {
					y = c[k];
					c[k] = c[k + 1];
					c[k + 1] = y;
					t = d[k];
					d[k] = d[k + 1];
					d[k + 1] = t;
				}
			}
		}
		for (i = 0; i <= 4; i++) {
			System.out.println("第" + (i + 1) + "名是第" + d[i] + "号选手，得分为" + c[i]);
		}
	}
}

（三）代码托管