Java Collections emptyMap() Method

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Description

The Java Collections emptyMap() method is used to get the empty map (immutable). This map is serializable.

Declaration

Following is the declaration for java.util.Collections.emptyMap() method.

public static final <K,V> Map<K,V> emptyMap()

Parameters

NA

Return Value

NA

Exception

NA

Getting Empty Map of String, Integer Pair Example

The following example shows the usage of Java Collection emptyMap() method to get an empty map of String, Integer pairs. We've created an empty map using emptyMap() method and then tried adding few elements to it which results in exception.

 
package com.tutorialspoint;

import java.util.Collections;
import java.util.Map;

public class CollectionsDemo {
   public static void main(String args[]) {
      
      // create an empty map    
      Map<String, Integer> emptyMap = Collections.emptyMap();

      System.out.println("Created empty immutable map: "+emptyMap);

      // try to add elements
      emptyMap.put("1", 1);
      emptyMap.put("2", 2);
   }    
}

Output

Let us compile and run the above program, this will produce the following result.Exception will be thrown as the map is immutable.

Created empty immutable map: {}
Exception in thread "main" java.lang.UnsupportedOperationException
	at java.base/java.util.AbstractMap.put(AbstractMap.java:209)
	at com.tutorialspoint.CollectionsDemo.main(CollectionsDemo.java:15)

Getting Empty Map of String, String Pair Example

The following example shows the usage of Java Collection emptyMap() method to get an empty map of String, String pairs. We've created an empty map using emptyMap() method and then tried adding few elements to it which results in exception.

 
package com.tutorialspoint;

import java.util.Collections;
import java.util.Map;

public class CollectionsDemo {
   public static void main(String args[]) {
      
      // create an empty map    
      Map<String, String> emptyMap = Collections.emptyMap();

      System.out.println("Created empty immutable map: "+emptyMap);

      // try to add elements
      emptyMap.put("1", "A");
      emptyMap.put("2", "B");
   }    
}

Output

Let us compile and run the above program, this will produce the following result.Exception will be thrown as the map is immutable.

Created empty immutable map: {}
Exception in thread "main" java.lang.UnsupportedOperationException
	at java.base/java.util.AbstractMap.put(AbstractMap.java:209)
	at com.tutorialspoint.CollectionsDemo.main(CollectionsDemo.java:15)

Getting Empty Map of String, Object Pair Example

The following example shows the usage of Java Collection emptyMap() method to get an empty map of String, Student object pairs. We've created an empty map using emptyMap() method and then tried adding few elements to it which results in exception.

 
package com.tutorialspoint;

import java.util.Collections;
import java.util.Map;

public class CollectionsDemo {
   public static void main(String args[]) {
      
      // create an empty map    
      Map<String, Object> emptyMap = Collections.emptyMap();

      System.out.println("Created empty immutable map: "+emptyMap);

      // try to add elements
      emptyMap.put("1", new Student(1, "Julie"));
      emptyMap.put("2", new Student(2, "Jene"));
   }    
}
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.Exception will be thrown as the map is immutable.

Created empty immutable map: {}
Exception in thread "main" java.lang.UnsupportedOperationException
	at java.base/java.util.AbstractMap.put(AbstractMap.java:209)
	at com.tutorialspoint.CollectionsDemo.main(CollectionsDemo.java:15)