1. 一个简单例子介绍关于Java HashMap 的基本操作:创建、添加、更新、删除及遍历。
2. 代码:
1 import java.util.*;
2
3 /**
4 * the basic usage of hashmap
5 * @author SheepCore
6 * @date 2020-03-03
7 */
8 public class Main {
9 public static void main(String[] args) {
10 //Created a hashmap and named it fruitStore
11 Map<String, Float> fruitStore = new HashMap<>();
12
13 //add some fruit with the tag <name, price> into fruitStore
14 fruitStore.put("Apple", 8.98f);
15 fruitStore.put("Dragon Fruit", 5.98f);
16 fruitStore.put("Red Grape", 6.98f);
17 fruitStore.put("Banana", 4.98f);
18 fruitStore.put("Durian", 32.8f);
19
20 //update the price of Apple
21 fruitStore.put("Apple", 7.50f);
22
23 //the store sold out all the banana, so remove it from the store
24 fruitStore.remove("Banana");
25 fruitStore.put("Orange", 4.85f);
26
27 //show all kinds of fruit in the store
28 Iterator iter = fruitStore.entrySet().iterator();
29 while (iter.hasNext()) {
30 Map.Entry entry = (Map.Entry)iter.next();
31 String name = (String)entry.getKey();
32 float price = (float)entry.getValue();
33 System.out.printf("%-15s %-5.2f
", name, price);
34 }
35
36 //count the average price of all fruit in the store
37 Iterator iter2 = fruitStore.values().iterator();
38 float sum = 0f;
39 while (iter2.hasNext()) {
40 sum += (float)iter2.next();
41 }
42 System.out.printf("Average Price: ¥%.2f
", sum / fruitStore.size());
43 }
44 }