Java Collections emptySet() Method

---

---

Description

The Java Collections emptySet() method is used to get the empty set (immutable). This set is serializable.

Declaration

Following is the declaration for java.util.Collections.emptySet() method.

public static final <T> Set<T> emptySet()

Parameters

NA

Return Value

NA

Exception

NA

Getting Empty Set of Integer Example

The following example shows the usage of Java Collection emptySet() method to get an empty set of Integers. We've created an empty set using emptySet() method and then tried adding few elements to it which results in exception.

 
package com.tutorialspoint;

import java.util.Collections;
import java.util.Set;

public class CollectionsDemo {
   public static void main(String args[]) {
      
      // create an empty set    
      Set<Integer> emptySet = Collections.emptySet();

      System.out.println("Created empty immutable set: "+emptySet);

      // try to add elements
      emptySet.add(1);
      emptySet.add(2);
   }    
}

Output

Let us compile and run the above program, this will produce the following result.Exception will be thrown as the list is immutable.

Created empty immutable set: []
Exception in thread "main" java.lang.UnsupportedOperationException
	at java.base/java.util.AbstractCollection.add(AbstractCollection.java:267)
	at com.tutorialspoint.CollectionsDemo.main(CollectionsDemo.java:15)

Getting Empty Set of String Example

The following example shows the usage of Java Collection emptySet() method to get an empty set of Strings. We've created an empty set using emptySet() method and then tried adding few elements to it which results in exception.

 
package com.tutorialspoint;

import java.util.Collections;
import java.util.Set;

public class CollectionsDemo {
   public static void main(String args[]) {
      
      // create an empty set    
      Set<String> emptySet = Collections.emptySet();

      System.out.println("Created empty immutable set: "+emptySet);

      // try to add elements
      emptySet.add("A");
      emptySet.add("B");
   }    
}

Output

Let us compile and run the above program, this will produce the following result.Exception will be thrown as the list is immutable.

Created empty immutable set: []
Exception in thread "main" java.lang.UnsupportedOperationException
	at java.base/java.util.AbstractCollection.add(AbstractCollection.java:267)
	at com.tutorialspoint.CollectionsDemo.main(CollectionsDemo.java:15)

Getting Empty Set of Object Example

The following example shows the usage of Java Collection emptySet() method to get an empty set of Student objects. We've created an empty set using emptySet() method and then tried adding few elements to it which results in exception.

 
package com.tutorialspoint;

import java.util.Collections;
import java.util.Set;

public class CollectionsDemo {
   public static void main(String args[]) {
      
      // create an empty set    
      Set<Student> emptySet = Collections.emptySet();

      System.out.println("Created empty immutable set: "+emptySet);

      // try to add elements
      emptySet.add(new Student(1, "Julie"));
      emptySet.add(new Student(2, "Robert"));
   }    
}
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
}

Output

Let us compile and run the above program, this will produce the following result.Exception will be thrown as the list is immutable.

Created empty immutable set: []
Exception in thread "main" java.lang.UnsupportedOperationException
	at java.base/java.util.AbstractCollection.add(AbstractCollection.java:267)
	at com.tutorialspoint.CollectionsDemo.main(CollectionsDemo.java:15)