5.1
 1 public class Demo {

     public static void main(String[] args) {

         // 创建一个输入对象

         java.util.Scanner input = new java.util.Scanner(System.in);

         System.out.print("Enter an integer,the input ends if it is 0: ");

         //输入一串整数以空格隔开，如果输入0，程序结束

         int num = input.nextInt();

         //定义正数与负数的个数变量，定义输入值得总和（不包括0）

         int positiveNum = 0, negativeNum = 0;

         double sum = 0;

         //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

         if (num != 0) {

             //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

             while (num != 0) {

                 if (num > 0)

                     positiveNum++;

                 else

                     negativeNum++;

                 sum += num;

                 num = input.nextInt();

             }

             //输出相应的正数、负数、总和和平均数的值

             System.out.println("The number of positives is " + positiveNum);

             System.out.println("The number of negatives is " + negativeNum);

             System.out.println("The total is " + sum);

             System.out.println("The average is " + sum

                     / (positiveNum + negativeNum));

         }else

             System.out.println("No numbers are entered except 0");

     }

 }

5.2
 1 public class Demo {

     public static void main(String[] args) {

         // 定义问题的数量为10

         final int NUMBER_OF_QUESTIONS = 10;

         // 定义变量存放正确的个数，定义变量存放循环次数

         int correctCount = 0;

         int count = 1;

         // 定义开始时间

         long startTime = System.currentTimeMillis();

         // 创建一个输入对象

         java.util.Scanner input = new java.util.Scanner(System.in);

         // 随机产生两个整数，循环10次

         while (count <= 10) {

             // 定义两个整数变量，存放随机产生的1~15内的整数

             int num1 = (int) (Math.random() * 15) + 1;

             int num2 = (int) (Math.random() * 15) + 1;

             // 输入答案

             System.out.print("What is " + num1 + " + " + num2 + "? ");

             int answer = input.nextInt();

             // 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

             if (num1 + num2 == answer) {

                 System.out.println("You are correct!");

                 correctCount++;

             } else

                 System.out.println("Your answer is wrong.\n" + num1 + " + "

                         + num2 + " should be " + (num1 + num2));

             // 循环次数加一

             count++;

         }

         // 定义结束时间

         long endTime = System.currentTimeMillis();

         // 计算测验时间

         long testTime = endTime - startTime;

         // 输出正确答案的个数与测验时间（单位秒）

         System.out.println("Correct count is " + correctCount

                 + "\nTest time is " + testTime / 1000 + " seconds");

     }

 }