Question

您将开发一个程序来计算生成范围中每个数字的次数。您的程序将生成[0,9]范围内的100个数字，您将打印一个类似于下图所示直方图的直方图。

 0  ********
 1  *********** 
 2  ******
 3  ****************
 4  **************
 5  *****
 6  ************
 7  ***********
 8  ********
 9  *********

要打印上面显示的直方图，您的程序必须记录每个数字的生成次数。

我正在尝试将num和count传递给print方法，然后将其传递给switch语句以将其打印为星号。但它给了我一个错误。建议？

以下是我遇到的错误：

必需：int，int found：无参数原因：实际和正式参数列表的长度不同/tmp/java_9JsuaS/RandomSrv.java:55：错误：类RandomSrv中的方法打印无法应用于给定类型; System.out.print（＆＃34; 9＆＃34; + this.print（））; ^

import java.util.Random;

public class RandomSrv
{

    public void genNums(int total)
    {

        for(int counter = 0; counter < total; counter++) //counter for the random gen nums//

        {
            int UPPER_BOUND = 10;//max number it will go to: 9

            int count0 = 0; //stores counter//

            int count1 = 0;
            int count2 = 0;

            int count3 = 0;

            int count4 = 0;

            int count5 = 0;

            int count6 = 0;

            int count7 = 0;

            int count8 = 0;

            int count9 = 0;

            int count = 0;

            Random randObj = new Random(); //creating randoms object//
            int num = randObj.nextInt(UPPER_BOUND);//num ranges 1-10//
            print(num, count);
            switch (num) //counts it into catagories//
                {
                case 0: count = count0++;
                    System.out.print("0 " + this.print());
                    break;
                case 1: count = count1++;
                    System.out.print("1 " + this.print());
                    break;
                case 2: count = count2++;
                    System.out.print("2 " + this.print());
                    break;
                case 3: count = count3++;
                    System.out.print("3 " + this.print());
                    break;
                case 4: count = count4++;
                    System.out.print("4 " + this.print());
                    break;
                case 5: count = count5++;
                    System.out.print("5 " + this.print());
                    break;
                case 6: count = count6++;
                    System.out.print("6 " + this.print());
                    break;
                case 7: count = count7++;
                    System.out.print("7 " + this.print());
                    break;
                case 8: count = count8++;
                    System.out.print("8 " + this.print());
                    break;
                case 9: count = count9++;
                    System.out.print("9 " + this.print());
                    break;
                }

        }
    }
    public void print(int num, int count) //converting them to astericks//
    {
    for(int x = 0; x < count; x++)
        {
        System.out.println("*");
        }       
    }
}

Answer 1

这是一种方法：

int[] counts = new int[10];   // this array will hold the count for each number (0-9)
Random rand = new Random();   // the Random object

/* Loop 100 times getting a random number each time, and add to the corresponding count */
for(int i=0; i<100; i++)
{
    switch(rand.nextInt(10))
    {
        case 0: counts[0]++; break;
        case 1: counts[1]++; break;
        case 2: counts[2]++; break;
        case 3: counts[3]++; break;
        case 4: counts[4]++; break;
        case 5: counts[5]++; break;
        case 6: counts[6]++; break;
        case 7: counts[7]++; break;
        case 8: counts[8]++; break;
        case 9: counts[9]++; break;
        default: break;
    }
}

/* Loop 10 times printing the asterisks for each count */
for(int i=0; i<10; i++)
{
     System.out.print(i + " ");
     for(int j=0; j<counts[i]; j++)
         System.out.print("*");
     System.out.println();
}

在此处运行（在线编译器）：http://rextester.com/UKSB96871

Answer 2

另一种解决方案

Map<Integer, String> groups = Stream.generate(() -> rand.nextInt(10))
                                    .limit(100)
                                    .collect(Collectors.groupingBy(Function.identity(),
                                                                   Collectors.mapping(e -> "*",
                                                                                      Collectors.joining())));

groups.forEach((number, hist) -> System.out.println(number + " " + hist));

Answer 3

我认为这是一种简单的方法：

import java.util.Random;

public class RandomSrv {
    private final int UPPER_BOUND;// max number it will go to
    private final int TOTAL;
    private final int[] numbers;
    private final int[] counter;

    public RandomSrv(int upperBound, int total) {
        this.UPPER_BOUND = upperBound;
        this.TOTAL = total;
        this.numbers = new int[this.TOTAL];
        this.counter = new int[this.UPPER_BOUND];
        this.genNums();
    }

    private void genNums() {
        Random randObj = new Random(); // creating random objects
        for (int counter = 0; counter < TOTAL; counter++) {
            // counter for the
            // random generate numbers
            int num = randObj.nextInt(UPPER_BOUND);
            this.numbers[counter] = num;
            this.counter[num]++;
        }
    }

    private void print(int count) // converting them to asterisks
    {
        System.out.print(String.format("%d: ", count));
        for (int x = 0; x < counter[count]; x++) {
            System.out.print("*");
        }
        System.out.println();
    }

    public void printAll() {
        for (int count = 0; count < this.UPPER_BOUND; count++) {
            this.print(count);
        }
    }

    public static void main(String[] commandArguments) {
        int upperBound = 10;
        int total = 100;
        new RandomSrv(upperBound, total).printAll();
    }
}

方法/打印随机数的直方图

3 个答案: