Hashtable
类实现将键映射到值的哈希表。 Hashtable类不允许null作为键或值。用作Hashtable类的键的对象必须实现hashCode
方法和equals
方法。
Hashtable中使用的基本方法是:
put()
- 将新元素(键值)添加到Hashtable中。get()
- 通过传递键返回值。remove()
- 从Hashtable中删除键和值。size()
- 返回Hashtable的大小。containsKey()
- 如果密钥存在于Hashtable中则返回true,否则返回false。containsValue()
- 如果Hashtable中存在值,则返回true,否则返回false。clear()
- 从Hashtable中删除所有元素。
文件:HashTableExample.java -
package com.yiibai.tutorial;
import java.util.Hashtable;
/**
* @author yiibai
*
*/
public class HashTableExample {
public static void main(String[] args) {
Hashtable<String String> hashtable=new Hashtable<>();
/*Adding key and values in Hashtable*/
hashtable.put("1" "One");
hashtable.put("2" "Two");
hashtable.put("3""Three");
hashtable.put("4" "Four");
hashtable.put("5" "Five");
System.out.println("Hashtable key-values are:"+hashtable);
/*Get value by key from the Hashtable*/
System.out.println("Value of '4' is: "+hashtable.get("4"));
/*Removing key and value from the Hashtable */
hashtable.remove("4");
System.out.println("After removal Hashtable Key-Value: " +hashtable);
/*Getting size of Hashtable*/
System.out.println("Size of Hashtable is : "+hashtable.size());
/*Checking if key exist in the Hashtable or not*/
System.out.println("Key '3' exist: "+hashtable.containsKey("3"));
/*Checking if value exist in the Hashtable or not*/
System.out.println("Key '6' exist: "+hashtable.containsValue("6"));
/*Remove all keys and values from the Hashtable*/
hashtable.clear();
System.out.println("After clearing Hashtable: "+hashtable);
}
}
执行上面示例代码,得到以下结果:
Hashtable key-values are:{5=Five 4=Four 3=Three 2=Two 1=One}
Value of '4' is: Four
After removal Hashtable Key-Value: {5=Five 3=Three 2=Two 1=One}
Size of Hashtable is : 4
Key '3' exist: true
Key '6' exist: false
After clearing Hashtable: {}