Question

Please teach me how to use function interface by java

● Write a functional interface StringOperator with the method performOperation
that takes two references to String objects as parameters.
● In a driver program, use lambda expressions to create two different objects that
implement the StringOperator interface.
○ One of them concatenates the two Strings, returning the new String
○ One of them sets the first String to all uppercase and the second String to all
lowercase and then concatenates them, returning the new String
● Test using both objects in a driver program.

Answer 1

//In case of any, queries, please revert back
public class Solution
{
   //we first declare an interface
   interface StringOperator
   {    //now we define operations or methods
  
       void performOperation(String message1,String message2);
   }

   public static void main(String args[])
   {
   //syntax for writing lambda functions
       StringOperator concat = (message1,message2) ->System.out.println(message1
                                               + message2);
   StringOperator concatModified=(message1,message2) ->System.out.println(message1.toUpperCase()
                                               + message2.toLowerCase());
      
concatModified.performOperation("Hello","World");
   concat.performOperation("Hello","World");
  
   }
}