- Java.util Package Classes
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- Java.util - ArrayDeque
- Java.util - ArrayList
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- Java.util - BitSet
- Java.util - Calendar
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- Java.util - Currency
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- 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 IdentityHashMap containsKey() Method
Description
The containsKey(Object key) method is used to test whether the specified object reference is a key in this identity hash map.
Declaration
Following is the declaration for java.util.IdentityHashMap.containsKey() method.
public boolean containsKey(Object key)
Parameters
key − This is the possible key to be checked.
Return Value
The method call returns 'true' if the specified object reference is a key in this map.
Exception
NA
Checking Key to Exist in an IdentityHashMap of Integer, Integer Pair Example
The following example shows the usage of Java IdentityHashMap containsKey() method to check if a key is present in a Map or not. We've created a Map object of Integer,Integer pairs. Then few entries are added, map is printed and using containsKey() we're checking about two keys in the map.
package com.tutorialspoint; import java.util.IdentityHashMap; public class IdentityHashMapDemo { public static void main(String args[]) { // create hash map IdentityHashMap<Integer,Integer> newmap = new IdentityHashMap<>(); // 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("Map contains 2 as key: " + newmap.containsKey(2)); System.out.println("Map contains 4 as key: " + newmap.containsKey(4)); } }
Output
Let us compile and run the above program, this will produce the following result.
Initial map elements: {2=2, 3=3, 1=1} Map contains 2 as key: true Map contains 4 as key: false
Checking Key to Exist in an IdentityHashMap of Integer, String Pair Example
The following example shows the usage of Java IdentityHashMap containsKey() method to check if a key is present in a Map or not. We've created a Map object of Integer,String pairs. Then few entries are added, map is printed and using containsKey() we're checking about two keys in the map.
package com.tutorialspoint; import java.util.IdentityHashMap; public class IdentityHashMapDemo { public static void main(String args[]) { // create hash map IdentityHashMap<Integer,String> newmap = new IdentityHashMap<>(); // 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("Map contains 2 as key: " + newmap.containsKey(2)); System.out.println("Map contains 4 as key: " + newmap.containsKey(4)); } }
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} Map contains 2 as key: true Map contains 4 as key: false
Checking Key to Exist in an IdentityHashMap of Integer, Object Pair Example
The following example shows the usage of Java IdentityHashMap containsKey() method to check if a key is present in a Map or not. We've created a Map object of Integer,Student pairs. Then few entries are added, map is printed and using containsKey() we're checking about two keys in the map.
package com.tutorialspoint; import java.util.IdentityHashMap; public class IdentityHashMapDemo { public static void main(String args[]) { // create hash map IdentityHashMap<Integer,Student> newmap = new IdentityHashMap<>(); // 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("Map contains 2 as key: " + newmap.containsKey(2)); System.out.println("Map contains 4 as key: " + newmap.containsKey(4)); } } 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 ]} Map contains 2 as key: true Map contains 4 as key: false
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