- Java.util Package Classes
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- Java.util - ArrayDeque
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- 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 HashMap isEmpty() Method
Description
The isEmpty() method is used to check if this map contains no key-value mappings.
Declaration
Following is the declaration for java.util.HashMap.isEmpty() method.
public boolean isEmpty()
Parameters
NA
Return Value
The method call returns 'true' if this map contains no key-value mappings.
Exception
NA
Checking Map of Integer, Integer Pair to be empty Example
The following example shows the usage of Java HashMap isEmpty() method to check a Map if it is empty or not. We've created a Map object of Integer,Integer pair. 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.HashMap; public class HashMapDemo { public static void main(String args[]) { // create hash map HashMap<Integer,Integer> newmap = new HashMap<>(); // populate hash 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: {1=1, 2=1, 3=1} Is map Empty: false Map elements after clear: {} Is map Empty: true
Checking Map of Integer, String Pair to be empty Example
The following example shows the usage of Java HashMap isEmpty() method to check a Map if it is empty or not. We've created a Map object of Integer,String pair. 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.HashMap; public class HashMapDemo { public static void main(String args[]) { // create hash map HashMap<Integer,String> newmap = new HashMap<>(); // populate hash 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: {1=tutorials, 2=point, 3=is best} Is map Empty: false Map elements after clear: {} Is map Empty: true
Checking Map of Integer, Student Pair to be empty Example
The following example shows the usage of Java HashMap isEmpty() method to check a Map if it is empty or not. We've created a Map object of Integer,Student pair. 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.HashMap; public class HashMapDemo { public static void main(String args[]) { // create hash map HashMap<Integer,Student> newmap = new HashMap<>(); // 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); 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 ], 2=[ 2, Robert ], 3=[ 3, Adam ]} Is map Empty: false Map elements after clear: {} Is map Empty: true
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