The
newSetFromMap() method of
java.util.Collections class is used to return a set backed by the specified map. The resulting set displays the same ordering, concurrency, and performance characteristics as the backing map. In essence, this factory method provides a Set implementation corresponding to any Map implementation. There is no need to use this method on a Map implementation that already has a corresponding Set implementation (such as HashMap or TreeMap).
Syntax:
public static Set newSetFromMap(Map map)
Parameters: This method takes the backing
map as a parameter
Return Value: This method returns the
set backed by the map
Exception: This method throws
IllegalArgumentException, if map is not empty.
Below are the examples to illustrate the
newSetFromMap() method
Example 1:
Output:
Map is: {C=true, B=true, A=true, D=true}
Set from Map is: [C, B, A, D]
Example 2: for
IllegalArgumentException
