Java HashMap clear() Method
Java HashMapThe clear() method is used to delete all key/value pairs in the specified HashMap.
The syntax of the clear() method is:
hashmap.clear()
Note:hashmap is an object of the HashMap class.
Parameter Description:
- None
Return Value
No return value.
Example
The following example demonstrates the use of the clear() method:
Example
class Main {
public static void main(String[] args) {
HashMap<Integer, String> sites = new HashMap<>();
sites.put(1, "Google");
sites.put(2, "Example");
sites.put(3, "Taobao");
System.out.println("HashMap: " + sites);
// Delete all mappings from the HashMap
sites.clear();
System.out.println("After using clear() method: " + sites);
}
}
Executing the above program outputs the result:
HashMap: {1=Google, 2=Example, 3=Taobao}
使用 clear() 方法后: {}
In the above example, we created a HashMap named sites, and later in the code we used the clear() method to delete all key/value pairs of sites.
Note: We can also useJava HashMap remove() Methodto delete the key-value pair corresponding to the key.
Reinitialize HashMap
In Java, we can also delete all key/value pairs by reinitializing the HashMap, for example:
Example
class Main {
public static void main(String[] args) {
HashMap<Integer, String> sites = new HashMap<>();
sites.put(1, "Google");
sites.put(2, "Example");
sites.put(3, "Taobao");
System.out.println("HashMap: " + sites);
// Delete all mappings from the HashMap
// Reinitialize hashmap
sites = new HashMap<>();
System.out.println("New HashMap: " + sites);
}
}
Executing the above program outputs the result:
HashMap: {1=Google, 2=Example, 3=Taobao}
新的 HashMap: {}
In the above example, we created a HashMap named sites, which contains 3 elements. Note this line:
numbers = new HashMap<>();
The above code does not delete all items from the HashMap; it creates a new HashMap and assigns it to sites. The original key-value pairs of sites will be reclaimed and deleted by the garbage collector.
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