5.1 1 public class Demo {
 2     public static void main(String[] args) {
 3         // 创建一个输入对象
 4         java.util.Scanner input = new java.util.Scanner(System.in);
 5         System.out.print("Enter an integer,the input ends if it is 0: ");
 6         //输入一串整数以空格隔开，如果输入0，程序结束
 7         int num = input.nextInt();
 8         //定义正数与负数的个数变量，定义输入值得总和（不包括0）
 9         int positiveNum = 0, negativeNum = 0;
10         double sum = 0;
11         //判断输入的第一个整数是否为0，如果不是，继续判断，如果是，直接else
12         if (num != 0) {
13             //读入的整数计算正数个数、负数个数、总和，直到读入为0跳出循环
14             while (num != 0) {
15                 if (num > 0)
16                     positiveNum++;
17                 else
18                     negativeNum++;
19                 sum += num;
20                 num = input.nextInt();
21             }
22             //输出相应的正数、负数、总和和平均数的值
23             System.out.println("The number of positives is " + positiveNum);
24             System.out.println("The number of negatives is " + negativeNum);
25             System.out.println("The total is " + sum);
26             System.out.println("The average is " + sum
27                     / (positiveNum + negativeNum));
28         }else
29             System.out.println("No numbers are entered except 0");
30     }
31 }

5.2 1 public class Demo {
 2     public static void main(String[] args) {
 3         // 定义问题的数量为10
 4         final int NUMBER_OF_QUESTIONS = 10;
 5         // 定义变量存放正确的个数，定义变量存放循环次数
 6         int correctCount = 0;
 7         int count = 1;
 8         // 定义开始时间
 9         long startTime = System.currentTimeMillis();
10         // 创建一个输入对象
11         java.util.Scanner input = new java.util.Scanner(System.in);
12         // 随机产生两个整数，循环10次
13         while (count <= 10) {
14             // 定义两个整数变量，存放随机产生的1~15内的整数
15             int num1 = (int) (Math.random() * 15) + 1;
16             int num2 = (int) (Math.random() * 15) + 1;
17             // 输入答案
18             System.out.print("What is " + num1 + " + " + num2 + "? ");
19             int answer = input.nextInt();
20             // 如果回答正确，正确的个数加一，回答不正确，输出正确的结果
21             if (num1 + num2 == answer) {
22                 System.out.println("You are correct!");
23                 correctCount++;
24             } else
25                 System.out.println("Your answer is wrong.\n" + num1 + " + "
26                         + num2 + " should be " + (num1 + num2));
27             // 循环次数加一
28             count++;
29         }
30         // 定义结束时间
31         long endTime = System.currentTimeMillis();
32         // 计算测验时间
33         long testTime = endTime - startTime;
34         // 输出正确答案的个数与测验时间（单位秒）
35         System.out.println("Correct count is " + correctCount
36                 + "\nTest time is " + testTime / 1000 + " seconds");
37     }
38 }