- Java.util Package Classes
- Java.util - Home
- Java.util - ArrayDeque
- Java.util - ArrayList
- Java.util - Arrays
- Java.util - BitSet
- Java.util - Calendar
- Java.util - Collections
- Java.util - Currency
- Java.util - Date
- Java.util - Dictionary
- Java.util - EnumMap
- Java.util - EnumSet
- Java.util - Formatter
- Java.util - GregorianCalendar
- Java.util - HashMap
- Java.util - HashSet
- Java.util - Hashtable
- Java.util - IdentityHashMap
- Java.util - LinkedHashMap
- Java.util - LinkedHashSet
- Java.util - LinkedList
- Java.util - ListResourceBundle
- Java.util - Locale
- Java.util - Observable
- Java.util - PriorityQueue
- Java.util - Properties
- Java.util - PropertyPermission
- Java.util - PropertyResourceBundle
- Java.util - Random
- Java.util - ResourceBundle
- Java.util - ResourceBundle.Control
- Java.util - Scanner
- Java.util - ServiceLoader
- Java.util - SimpleTimeZone
- Java.util - Stack
- Java.util - StringTokenizer
- Java.util - Timer
- Java.util - TimerTask
- Java.util - TimeZone
- Java.util - TreeMap
- Java.util - TreeSet
- Java.util - UUID
- Java.util - Vector
- Java.util - WeakHashMap
- Java.util Package Extras
- Java.util - Interfaces
- Java.util - Exceptions
- Java.util - Enumerations
- Java.util Useful Resources
- Java.util - Useful Resources
- Java.util - Discussion
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)
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