Java 程序计算数组中每个元素的频率

在本文中，我们将展示如何使用 for 循环编写一个 Java 程序来计算数组中每个元素的频率。

package NumPrograms;

import java.util.Arrays;
import java.util.Scanner;

public class ArrayCountOccrenceAll1 {
	private static Scanner sc;
	
	public static void main(String[] args) {
		int Size, i, j, count;
		
		sc = new Scanner(System.in);
		
		System.out.print("Please Enter Frequency Array size = ");
		Size = sc.nextInt();
		
		int[] arr = new int[Size];
		int[] freq = new int[Size];
		Arrays.fill(freq, -1);
		
		System.out.format("Enter Frequency Array %d elements : ", Size);
		for(i = 0; i < Size; i++) 
		{
			arr[i] = sc.nextInt();
		}
		
		for(i = 0; i < arr.length; i++)
		{
			count = 1;
			for(j = i + 1; j < arr.length; j++)
			{
				if(arr[i] == arr[j])
				{
					count++;
					freq[j] = 0;
				}
			}
			if(freq[i] != 0)
			{
				freq[i] = count;
			}
		}
		System.out.println("The Frequency of All the Elements in this Array ");
		
		for(i = 0; i < arr.length; i++) 
		{
			if(freq[i] != 0)
			{
				System.out.println(arr[i] + " Occurs " + freq[i] + " Times.");
			}
		}
	}
}

此 程序 使用 HashMap 来计算数组中每个元素或所有元素的频率。

package NumPrograms;

import java.util.*;

public class ArrayCountOccrenceAll2 {
	private static Scanner sc;
	
	public static void main(String[] args) {
		
		sc = new Scanner(System.in);
		
		System.out.print("Please Enter size = ");
		int Size = sc.nextInt();
		
		int[] arr = new int[Size];
		
		System.out.format("Enter %d elements : ", Size);
		for(int i = 0; i < Size; i++) 
		{
			arr[i] = sc.nextInt();
		}

		System.out.println("The Frequency of All the Elements in this Array ");
		arrFreq(arr);

	}
	static void arrFreq(int arr[]) {
		Map<Integer, Integer> countFreq = new HashMap<>();
		
		for(int i : arr)
		{
			if(countFreq.containsKey(i))
			{
				countFreq.put(i, countFreq.get(i) + 1);
			}
			else
			{
				countFreq.put(i, 1);
			}
		}
		
		for(Map.Entry<Integer, Integer> entry: countFreq.entrySet())
		{
			System.out.println(entry.getKey() + " Occurs " + entry.getValue() + " Times.");
		}
	}
}

Please Enter size = 7
Enter 7 elements : 22 9 22 5 9 11 14
The Frequency of All the Elements in this Array 
5 Occurs 1 Times.
22 Occurs 2 Times.
9 Occurs 2 Times.
11 Occurs 1 Times.
14 Occurs 1 Times.