- Java.util Package Classes
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- Java.util - HashMap
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- Java.util - IdentityHashMap
- Java.util - LinkedHashMap
- Java.util - LinkedHashSet
- Java.util - LinkedList
- Java.util - ListResourceBundle
- Java.util - Locale
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- Java.util - Properties
- Java.util - PropertyPermission
- Java.util - PropertyResourceBundle
- Java.util - Random
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- 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
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- Java.util - WeakHashMap
- Java.util Package Extras
- Java.util - Interfaces
- Java.util - Exceptions
- Java.util - Enumerations
- Java.util Useful Resources
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- Java.util - Discussion
Java IdentityHashMap isEmpty() Method
Description
The isEmpty() method is used to test if this identity hash map contains no key-value mappings.
Declaration
Following is the declaration for java.util.IdentityHashMap.isEmpty() method.
public boolean isEmpty()
Parameters
NA
Return Value
The method call returns 'true' if this identity hash map contains no key-value mappings.
Exception
NA
Checking emptyness of IdentityHashMap of Integer, Integer Pair Example
The following example shows the usage of Java IdentityHashMap isEmpty() method to check a Map if it is empty or not. We've created a Map object of Integer,Integer pairs. Then few entries are added, map is printed. Then map is checked using isEmpty() method. Using clear() method, map is cleared and printed again and checked again using isEmpty() method.
package com.tutorialspoint; import java.util.IdentityHashMap; public class IdentityHashMapDemo { public static void main(String args[]) { // create identity map IdentityHashMap<Integer,Integer> newmap = new IdentityHashMap<>(); // populate identity map newmap.put(1, 1); newmap.put(2, 2); newmap.put(3, 3); System.out.println("Initial map elements: " + newmap); System.out.println("Is map Empty: " + newmap.isEmpty()); // clear hash map newmap.clear(); System.out.println("Map elements after clear: " + newmap); System.out.println("Is map Empty: " + newmap.isEmpty()); } }
Output
Let us compile and run the above program, this will produce the following result.
Initial map elements: {2=2, 3=3, 1=1} Is map Empty: false Map elements after clear: {} Is map Empty: true
Checking emptyness of IdentityHashMap of Integer, String Pair Example
The following example shows the usage of Java IdentityHashMap isEmpty() method to check a Map if it is empty or not. We've created a Map object of Integer,String pairs. Then few entries are added, map is printed. Then map is checked using isEmpty() method. Using clear() method, map is cleared and printed again and checked again using isEmpty() method.
package com.tutorialspoint; import java.util.IdentityHashMap; public class IdentityHashMapDemo { public static void main(String args[]) { // create identity map IdentityHashMap<Integer,String> newmap = new IdentityHashMap<>(); // populate identity map newmap.put(1, "tutorials"); newmap.put(2, "point"); newmap.put(3, "is best"); System.out.println("Initial map elements: " + newmap); System.out.println("Is map Empty: " + newmap.isEmpty()); // clear hash map newmap.clear(); System.out.println("Map elements after clear: " + newmap); System.out.println("Is map Empty: " + newmap.isEmpty()); } }
Output
Let us compile and run the above program, this will produce the following result.
Initial map elements: {2=point, 3=is best, 1=tutorials} Is map Empty: false Map elements after clear: {} Is map Empty: true
Checking emptyness of IdentityHashMap of Integer, Object Pair Example
The following example shows the usage of Java IdentityHashMap isEmpty() method to check a Map if it is empty or not. We've created a Map object of Integer,Student pairs. Then few entries are added, map is printed. Then map is checked using isEmpty() method. Using clear() method, map is cleared and printed again and checked again using isEmpty() method.
package com.tutorialspoint; import java.util.IdentityHashMap; public class IdentityHashMapDemo { public static void main(String args[]) { // create identity map IdentityHashMap<Integer,Student> newmap = new IdentityHashMap<>(); // populate identity 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); System.out.println("Is map Empty: " + newmap.isEmpty()); // clear hash map newmap.clear(); System.out.println("Map elements after clear: " + newmap); System.out.println("Is map Empty: " + newmap.isEmpty()); } } 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: {1=[ 1, Julie ], 3=[ 3, Adam ], 2=[ 2, Robert ]} Is map Empty: false Map elements after clear: {} Is map Empty: true
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