Java Utility Library

Java Collections - singletonMap() Method

The java.util.Collections.singletonMap() method returns an immutable map, mapping only the specified key to the specified value. The returned map is serializable.

Syntax

public static <K,V> Map<K,V> singletonMap(K key, 
                                          V value)

Here, K and V are the type of key and value respectively maintained by the map.

Parameters

`key`	Specify the class of the map keys.
`value`	Specify the class of the map values.

Return Value

Returns an immutable map containing only the specified key-value mapping.

Exception

NA.

Example:

In the example below, the java.util.Collections.singletonMap() method returns an immutable map containing only the specified key-value mapping.

import java.util.*;

public class MyClass {
  public static void main(String[] args) {
    //creating a map
    Map<Integer, String> MyMap = new TreeMap<Integer, String>();

    //populating MyMap
    MyMap.put(102, "John");
    MyMap.put(101, "Marry");
    MyMap.put(103, "Kim");

    //printing the map
    System.out.println("MyMap contains: " + MyMap);

    //creating singleton map
    MyMap = Collections.singletonMap(100, "Hundred");

    //printing the map
    System.out.println("MyMap contains: " + MyMap);
  }
}

The output of the above code will be:

MyMap contains: {101=Marry, 102=John, 103=Kim}
MyMap contains: {100=Hundred}

❮ Java.util - Collections