- 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 HashSet clear() Method
Description
The Java HashSet clear() method is used to remove all of the elements from this set. The set will be empty after this call returns.
Declaration
Following is the declaration for java.util.HashSet.clear() method.
public void clear()
Parameters
NA
Return Value
NA
Exception
NA
Clearing a HashSet of Integers Example
The following example shows the usage of Java HashSet clear() method to remove entries from the HashSet. We've created a HashSet object of Integer. Then few entries are added using add() method and then set is printed. Now set is cleared using clear() method and printed again.
package com.tutorialspoint; import java.util.HashSet; public class HashSetDemo { public static void main(String args[]) { // create hash set HashSet <Integer> newset = new HashSet <>(); // populate hash set newset.add(1); newset.add(2); newset.add(3); // checking elements in hash set System.out.println("Hash set values: "+ newset); // clear the set newset.clear(); // print the set System.out.println("Hash set values after clearing: "+ newset); } }
Output
Let us compile and run the above program, this will produce the following result.
Hash set values: [1, 2, 3] Hash set values after clearing: []
Clearing a HashSet of Strings Example
The following example shows the usage of Java HashSet clear() method to remove entries from the HashSet. We've created a HashSet object of Strings. Then few entries are added using add() method and then set is printed. Now set is cleared using clear() method and printed again.
package com.tutorialspoint; import java.util.HashSet; public class HashSetDemo { public static void main(String args[]) { // create hash set HashSet <String> newset = new HashSet <>(); // populate hash set newset.add("Learning"); newset.add("Easy"); newset.add("Simply"); // checking elements in hash set System.out.println("Hash set values: "+ newset); // clear the set newset.clear(); // print the set System.out.println("Hash set values after clearing: "+ newset); } }
Output
Let us compile and run the above program, this will produce the following result.
Hash set values: [Learning, Easy, Simply] Hash set values after clearing: []
Clearing a HashSet of Objects Example
The following example shows the usage of Java HashSet clear() method to remove entries from the HashSet. We've created a HashSet object of Student objects. Then few entries are added using add() method and then set is printed. Now set is cleared using clear() method and printed again.
package com.tutorialspoint; import java.util.HashSet; public class HashSetDemo { public static void main(String args[]) { // create hash set HashSet <Student> newset = new HashSet <>(); // populate hash set newset.add(new Student(1, "Julie")); newset.add(new Student(2, "Robert")); newset.add(new Student(3, "Adam")); // checking elements in hash set System.out.println("Hash set values: "+ newset); // clear the set newset.clear(); // print the set System.out.println("Hash set values after clearing: "+ newset); } } 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.
Hash set values: [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ]] Hash set values after clearing: []
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