Hashtable clear() Method in Java

 

코딩하던 중 여러 hashTable을 사용하게 되었다. 한 3개??

 

재사용하기 위해서 메소드 찾아보던 중 clear() 라는 걸 발견

 

The java.util.Hashtable.clear() method in Java is used to clear and remove all of the keys from a specified Hashtable.

Syntax:

Hash_table.clear()

Parameters: The method does not accept any parameters.

Return Value: The method does not return any value.

 

 

// Java code to illustrate the clear() method 
import java.util.*; 

public class Hash_Table_Demo { 
	public static void main(String[] args) 
	{ 

		// Creating an empty Hashtable 
		Hashtable<Integer, String> hash_table = new Hashtable<Integer, String>(); 

		// Inserting Values into table 
		hash_table.put(10, "Geeks"); 
		hash_table.put(15, "4"); 
		hash_table.put(20, "Geeks"); 
		hash_table.put(25, "Welcomes"); 
		hash_table.put(30, "You"); 

		// Displaying the Hashtable 
		System.out.println("The Hashtable is: " + hash_table); 

		// Clearing the hash table using clear() 
		hash_table.clear(); 

		// Displaying the final Hashtable 
		System.out.println("Finally the table looks like this: " + hash_table); 
	} 
} 

 

 

OutPut-> 

The Hashtable is: {10=Geeks, 20=Geeks, 30=You, 15=4, 25=Welcomes}

Finally the table looks like this: {}

 

 

+ ************************************************************ 

사용했던 hashTable을 다시 사용하려면 ... 

clear() 가 아니라 

hash_table = new Hashtable<String, String>(); 
hash_table2 = new Hashtable<String, String>(); 
hash_table = resultString; 

 

이런식으로 사용한다.  중요! 

 

 

참고 https://www.geeksforgeeks.org/hashtable-clear-method-in-java/

Hashtable clear() Method in Java - GeeksforGeeks

 

https://stackoverflow.com/questions/35559129/why-does-clear-hashmap-method-clears-added-map-in-array-list