java - 在 HashMap 中显示问题

Question

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;

public class mainClass
{
    static Scanner keyboard = new Scanner(System.in);
    static HashMap <Integer[], String> hMap;

    public static void createAHashMap()
    {
        System.out.print("Express the initial capacity: ");
        int initialCapacity = keyboard.nextInt();
        System.out.print("Express the load factor: ");
        float loadFactor = keyboard.nextFloat();
        hMap = new HashMap <Integer[], String> (initialCapacity, loadFactor);       
    }

    public static void insertProductInformations()
    {
        Integer values[] = new Integer[3];
        System.out.print("\nEnter product's barcode number: ");
        values[0] = keyboard.nextInt();
        System.out.print("Enter product's name: ");
        String productName = keyboard.next();   
        System.out.print("Enter product's amount: ");
        values[1] = keyboard.nextInt();
        System.out.print("Enter product's price: ");
        values[2] = keyboard.nextInt(); 
        hMap.put(values, productName);
    }

    public static void displayList()
    {
        Set set = hMap.entrySet();
        Iterator iterator = set.iterator();
        System.out.println("\nBarcode Number\tProduct Amount\tProduct Price\tProduct Name");        
        while (iterator.hasNext()) 
        {
            Map.Entry mEntry = (Map.Entry) iterator.next();
            System.out.print(mEntry.getKey() + "\t\t" + mEntry.getValue() + "\n");
        }
    }

    public static void main(String[] args)
    {
        createAHashMap();
        System.out.print("\nEnter to add product '1'\n");
        System.out.print("Enter to display products '2'\n");
        System.out.print("Enter your choice: ");
        int entry = keyboard.nextInt();     
        while (entry != -99)
        {
            if (entry == 1)
            {
                insertProductInformations();
            }
            if (entry == 2)
            {
                displayList();
            }
            System.out.print("\nExpress your new choice (Exit: -99): ");
            entry = keyboard.nextInt();
        }       
    }
}

嗨!

我创建了一个包含超市产品信息的 HashMap 。但是，我无法正确显示我的键值(这是一个数组)。它向我显示了除产品名称外无关紧要的内容。我该如何纠正这个问题？

Answer 1

static HashMap <Integer[], String> hMap;

数组不适合作为 HashMap 中的键，因为具有完全相同元素的两个不同数组实例将被视为不同的键。此行为是由于数组不覆盖 Object 的事实造成的的 equals方法，所以两个数组 arr1和 arr2仅当 arr1==arr2 时才相等.

key 的打印不是您的主要问题。这可以通过使用 Arrays.toString 轻松解决。打印数组键。

我建议你改变你的HashMap至 HashMap<List<Integer>, String> .