- Java.util Package Classes
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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 remove() Method
Description
The Java HashMap remove() method is used to remove the mapping for the specified key from this map if present.
Declaration
Following is the declaration for java.util.HashMap.remove() method.
public V remove(Object key)
Parameters
key − This is the key whose mapping is to be removed from the map.
Return Value
The method call returns the previous value associated with key, or null if there was no mapping for key.
Exception
NA
Removing a key,value pair from a HashMap of Integer, Integer Pair Example
The following example shows the usage of Java HashMap remove() method to remove an entry from a Map. We've created a Map object of Integer,Integer pair. Then few entries are added, map is printed. Using remove() method, an entry is removed from the map and map is printed again.
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, 3); newmap.put(3, 3); System.out.println("Initial map elements: " + newmap); // remove one entry newmap.remove(2); System.out.println("Map elements after removing an entry: " + newmap); } }
Output
Let us compile and run the above program, this will produce the following result.
Initial map elements: {1=1, 2=3, 3=3} Map elements after removing an entry: {1=1, 3=3}
Removing a key,value pair from a HashMap of Integer, String Pair Example
The following example shows the usage of Java HashMap remove() method to remove an entry from a Map. We've created a Map object of Integer,String pair. Then few entries are added, map is printed. Using remove() method, an entry is removed from the map and map is printed again.
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); // remove one entry newmap.remove(2); System.out.println("Map elements after removing an entry: " + newmap); } }
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} Map elements after removing an entry: {1=tutorials, 3=is best}
Removing a key,value pair from a HashMap of Integer, Student Pair Example
The following example shows the usage of Java HashMap remove() method to remove an entry from a Map. We've created a Map object of Integer,Student. Then few entries are added, map is printed. Using remove() method, an entry is removed from the map and map is printed again.
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); // remove one entry newmap.remove(2); System.out.println("Map elements after removing an entry: " + 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: {1=[ 1, Julie ], 2=[ 2, Robert ], 3=[ 3, Adam ]} Map elements after removing an entry: {1=[ 1, Julie ], 3=[ 3, Adam ]}
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