The singletonMap() method of java.util.Collections class is used to return an immutable map, mapping only the specified key to the specified value. The returned map is serializable.
Syntax:
public static Map singletonMap(K key, V value)
Parameters: This method takes the following parameters as a argument:
- key – the sole key to be stored in the returned map.
- value – the value to which the returned map maps key.
Return Value: This method returns an immutable map containing only the specified key-value mapping.
Below are the examples to illustrate the singletonMap() method
Example 1:
Java
// Java program to demonstrate// singletonMap() method// for <String, String> Valueimport java.util.*;public class GFG1 { public static void main(String[] argv) throws Exception { try { // create singleton map // using singletonMap() method Map<String, String> map = Collections .singletonMap("key", "Value"); // printing the singletonMap System.out.println("Singleton map is: " + map); } catch (IllegalArgumentException e) { System.out.println("Exception thrown : " + e); } }} |
Output:
Singleton map is: {key=Value}
Example 2:
Java
// Java program to demonstrate// singletonMap() method// for <Integer, Boolean> Valueimport java.util.*;public class GFG1 { public static void main(String[] argv) throws Exception { try { // create singleton map // using singletonMap() method Map<Integer, Boolean> map = Collections .singletonMap(100, true); // printing the singletonMap System.out.println("Singleton map is: " + map); } catch (IllegalArgumentException e) { System.out.println("Exception thrown : " + e); } }} |
Output:
Singleton map is: {100=true}
