- Java.util Package Classes
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- Java.util - ArrayDeque
- Java.util - ArrayList
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- 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 WeakHashMap clear() Method
Description
The Java WeakHashMap clear() method is used to removes all mappings from this map.
Declaration
Following is the declaration for java.util.WeakHashMap.clear() method.
public void clear()
Parameters
NA
Return Value
NA
Exception
NA
Clearing a WeakHashMap of Integer, Integer Pairs Example
The following example shows the usage of Java WeakHashMap clear() method to clear a Map. We've created a Map object of Integer,Integer. Then few entries are added, map is printed. Using clear() method, map is cleared and printed again.
package com.tutorialspoint; import java.util.WeakHashMap; public class WeakHashMapDemo { public static void main(String args[]) { // create hash map WeakHashMap<Integer,Integer> newmap = new WeakHashMap<>(); // populate hash map newmap.put(1, 1); newmap.put(2, 2); newmap.put(3, 3); System.out.println("Initial map elements: " + newmap); // clear hash map newmap.clear(); System.out.println("Map elements after clear: " + newmap); } }
Output
Let us compile and run the above program, this will produce the following result.
Initial map elements: {3=3, 2=2, 1=1} Map elements after clear: {}
Clearing a WeakHashMap of Integer, String Pairs Example
The following example shows the usage of Java WeakHashMap clear() method to clear a Map. We've created a Map object of Integer,String. Then few entries are added, map is printed. Using clear() method, map is cleared and printed again.
package com.tutorialspoint; import java.util.WeakHashMap; public class WeakHashMapDemo { public static void main(String args[]) { // create hash map WeakHashMap<Integer,String> newmap = new WeakHashMap<>(); // populate hash map newmap.put(1, "tutorials"); newmap.put(2, "point"); newmap.put(3, "is best"); System.out.println("Initial map elements: " + newmap); // clear hash map newmap.clear(); System.out.println("Map elements after clear: " + newmap); } }
Output
Let us compile and run the above program, this will produce the following result.
Initial map elements: {3=is best, 2=point, 1=tutorials} Map elements after clear: {}
Clearing a WeakHashMap of Integer, Object Pairs Example
The following example shows the usage of Java WeakHashMap clear() method to clear a Map. We've created a Map object of Integer,Student pairs. Then few entries are added, map is printed.
package com.tutorialspoint; import java.util.WeakHashMap; public class WeakHashMapDemo { public static void main(String args[]) { // create hash map WeakHashMap<Integer,Student> newmap = new WeakHashMap<>(); // populate hash map newmap.put(1, new Student(1, "Julie")); newmap.put(2, new Student(2, "Robert")); newmap.put(3, new Student(3, "Adam")); System.out.println("Initial map elements: " + newmap); // clear hash map newmap.clear(); System.out.println("Map elements after clear: " + newmap); } } 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 map elements: {3=[ 3, Adam ], 2=[ 2, Robert ], 1=[ 1, Julie ]} Map elements after clear: {}
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