hashmaptreemap的用法
时间: 2023-12-26 07:27:58 浏览: 17
HashMap和TreeMap都是Java中的集合类,用于存储键值对。它们的用法如下:
1. HashMap的用法:
HashMap是基于哈希表的实现,它使用键对象的哈希码来进行存储和检索。以下是HashMap的用法示例:
```java
import java.util.HashMap;
public class Main {
public static void main(String[] args) {
// 创建一个HashMap对象
HashMap<String, Integer> hashMap = new HashMap<>();
// 添加键值对
hashMap.put("apple", 1);
hashMap.put("banana", 2);
hashMap.put("orange", 3);
// 获取键对应的值
int value = hashMap.get("banana");
System.out.println("Value of 'banana': " + value); // 输出:Value of 'banana': 2
// 检查是否包含某个键
boolean containsKey = hashMap.containsKey("apple");
System.out.println("Contains key 'apple': " + containsKey); // 输出:Contains key 'apple': true
// 删除键值对
hashMap.remove("orange");
// 遍历HashMap
for (String key : hashMap.keySet()) {
int val = hashMap.get(key);
System.out.println(key + ": " + val);
}
}
}
```
2. TreeMap的用法:
TreeMap是基于红黑树的实现,它会对键进行排序。以下是TreeMap的用法示例:
```java
import java.util.TreeMap;
public class Main {
public static void main(String[] args) {
// 创建一个TreeMap对象
TreeMap<String, Integer> treeMap = new TreeMap<>();
// 添加键值对
treeMap.put("apple", 1);
treeMap.put("banana", 2);
treeMap.put("orange", 3);
// 获取键对应的值
int value = treeMap.get("banana");
System.out.println("Value of 'banana': " + value); // 输出:Value of 'banana': 2
// 检查是否包含某个键
boolean containsKey = treeMap.containsKey("apple");
System.out.println("Contains key 'apple': " + containsKey); // 输出:Contains key 'apple': true
// 删除键值对
treeMap.remove("orange");
// 遍历TreeMap
for (String key : treeMap.keySet()) {
int val = treeMap.get(key);
System.out.println(key + ": " + val);
}
}
}
```
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