java - 我无法跟踪变量计数的增加

Question

我试图获取一个名为FrequencyCounters 的数组，计算一个数字在名为array 的数组中重复的次数。索引应该指的是数字，即索引 0 计算 0 出现的次数，索引 1 计算 1 出现的次数。它有点有效，但并不完美。

import java.util.*;

class ArrayTest {
    public static void main(String[] args) {
        int[] array = new int[]{1, 1, 4, 4, 4, 5, 5, 5, 5, 7, 8, 8, 8, 8, 9};

        Arrays.sort(array);
        int max = array[array.length - 1];
        int[] frequencyCounter = new int[max];
        System.out.println("max is " + max);
        int checkNumber = 1;
        int index = 0;
        int length = array.length - 1;
        for (int i = 0; i <= 8; i++) {
            System.out.println("i is " + i);
            if (index == 0) {
                System.out.println("running index=0 statement");
                while (checkNumber == array[index]) {

                    if (i == 0) {
                        System.out.println("Running i==0 statement");
                        frequencyCounter[i] = frequencyCounter[i] + 1;
                    } else if (i != 0) {
                        System.out.println("Running i!=0 statement");
                        frequencyCounter[i - 1] = frequencyCounter[i - 1] + 1;
                    }

                    index = index + 1;


                }
                checkNumber = checkNumber + 1;
            } else {

                System.out.println("index is " + index);
                System.out.println("running i=0 else statement");

                while (checkNumber == array[index]) {

                    if (i == 0) {
                        System.out.println("Running i==0 statement");
                        frequencyCounter[i] = frequencyCounter[i] + 1;
                    } else {
                        System.out.println("Running i!=0 statement");
                        frequencyCounter[i - 1] = frequencyCounter[i - 1] + 1;
                    }

                    index = index + 1;
                }
                checkNumber = checkNumber + 1;
            }
            System.out.println("index is " + index + " at end of loop for");
        }
        int output = 1;
        for (int Z = 0; Z <= 8; Z++) {


            System.out.printf("The number %d repeats %d  


                    times",output,frequencyCounter[Z]             
                    output++;
        }
    }


}

由于某种原因，在我的输出语句中索引突然从 5 跳到 9，然后跳到 14。我是一名高中生，希望在这个问题上得到一些帮助:)我需要找到数组的模式。我不允许使用像 HashMap 这样的花哨的东西。我只能使用数组类和循环进行简单的操作。

Answer 1

您可以创建一个数组，其大小为原始数组中最大 int (+1) 的大小，循环该数组，计算每个 int 出现的次数并将计数放在索引上。

public static void main(String[] args) {
    int [] array=new int[] {1,1,4,4,4,5,5,5,5,7,8,8,8,8,9};
    // replace the next line with sth else to get the max of the array.
    int max = Arrays.stream(array).max().getAsInt();
    int[] res = new int[max + 1];
    for (int i = 0; i < res.length; i++) {
        res[i] = 0;
        for (int anArray : array) {
            res[i] += anArray == i ? 1 : 0;
        }
    }
    /* for (int re : res) {
        System.out.println(re);
    } */
}