- 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 Hashtable clear() Method
Description
The Java Hashtable clear() method is used to clear this hashtable so that it contains no keys.
Declaration
Following is the declaration for java.util.Hashtable.clear() method.
public void clear()
Parameters
NA
Return Value
NA
Exception
NA
Clearing a HashTable of Integer, Integer Pair Example
The following example shows the usage of Java Hashtable clear() method to clear a Hashtable. We've created a Hashtable object of Integer,Integer pairs. Then few entries are added, table is printed. Using clear() method, table is cleared and printed again.
package com.tutorialspoint; import java.util.Hashtable; public class HashtableDemo { public static void main(String args[]) { // create hash table Hashtable<Integer,Integer> hashtable = new Hashtable<>(); // populate hash table hashtable.put(1, 1); hashtable.put(2, 2); hashtable.put(3, 3); System.out.println("Initial table elements: " + hashtable); // clear hash table hashtable.clear(); System.out.println("Hashtable elements after clear: " + hashtable); } }
Output
Let us compile and run the above program, this will produce the following result.
Initial table elements: {3=3, 2=2, 1=1} Hashtable elements after clear: {}
Clearing a HashTable of Integer, String Pair Example
The following example shows the usage of Java Hashtable clear() method to clear a Hashtable. We've created a Hashtable object of Integer,String pairs. Then few entries are added, table is printed. Using clear() method, table is cleared and printed again.
package com.tutorialspoint; import java.util.Hashtable; public class HashtableDemo { public static void main(String args[]) { // create hash table Hashtable<Integer,String> hashtable = new Hashtable<>(); // populate hash table hashtable.put(1, "tutorials"); hashtable.put(2, "point"); hashtable.put(3, "is best"); System.out.println("Initial table elements: " + hashtable); // clear hash table hashtable.clear(); System.out.println("Hashtable elements after clear: " + hashtable); } }
Output
Let us compile and run the above program, this will produce the following result.
Initial table elements: {3=is best, 2=point, 1=tutorials} Hashtable elements after clear: {}
Clearing a HashTable of Integer, Object Pair Example
The following example shows the usage of Java Hashtable clear() method to clear a Hashtable. We've created a Hashtable object of Integer,Student pairs. Then few entries are added, table is printed.
package com.tutorialspoint; import java.util.Hashtable; public class HashtableDemo { public static void main(String args[]) { // create hash table Hashtable<Integer,Student> hashtable = new Hashtable<>(); // populate hash table hashtable.put(1, new Student(1, "Julie")); hashtable.put(2, new Student(2, "Robert")); hashtable.put(3, new Student(3, "Adam")); System.out.println("Initial table elements: " + hashtable); // clear hash table hashtable.clear(); System.out.println("Hashtable elements after clear: " + hashtable); } } 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.
Initial table elements: {3=[ 3, Adam ], 2=[ 2, Robert ], 1=[ 1, Julie ]} Hashtable elements after clear: {}
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