java.util.HashSet isEmpty()
Description
The HashSet as majority of the Collection classes make use of Generics such that if we have declared our set like HashSet set = new HashSet() then the elements of inside our set is of type String. And we cannot insert different object type not unless its a subclass of the object declaration, otherwise a runtime error will be thrown.
The HashSet elements are unique, there would be no two identical elements that can exist.
Important notes for isEmpty() method:
- specified by isEmpty in interface Collection
- specified by isEmpty in interface Set
- overrides isEmpty in class AbstractCollection
Method Syntax
public boolean isEmpty()
Method Argument
| Data Type | Parameter | Description |
|---|---|---|
| N/A | N/A | N/A |
Method Returns
The isEmpty() method returns true if this set contains no elements.
Compatibility
Requires Java 1.2 and up
Java HashSet isEmpty() Example
Below is a java code demonstrates the use of isEmpty() method of HashSet class. The example presented might be simple however it shows the behavior of the isEmpty() method.
package com.javatutorialhq.java.examples;
import static java.lang.System.*;
import java.util.HashSet;
/*
* This example source code demonstrates the use of
* isEmpty() method of HashSet class
*/
public class HashSetIsEmptyExample {
public static void main(String[] args) throws InterruptedException {
// get the HashMap object from the method init()
HashSet studentSet = init();
// validate the contents of our set
if(studentSet.isEmpty()){
out.println("student database is empty");
}
else{
out.println("student database has "+studentSet.size()+" names");
}
}
private static HashSet init() {
// declare the HashSet object
HashSet studentSet = new HashSet<>();
// put contents to our HashMap
studentSet.add("Shyra Travis");
studentSet.add("Sharon Wallace");
studentSet.add("Leo Batista");
return studentSet;
}
}
There are two methods created on the above example, main() and init. The main method calls the init() which initializes and assign values to a HashSet object. The main() method assign to a new HashSet object the returned object by the init() method. We use the isEmpty method to validate our HashSet if its empty or not.
Sample Output
Below is the sample output when you run the above example.
