Introduction

• Supplier interface is a functional interface in Java 8 that represents a supplier of results and takes no input arguments.
• It is part of the java.util.function package.

• Uses of Supplier Interface:
  • Used to generate or supply data without any input.
  • Commonly used for lazy evaluation or on-demand object creation.
  • Helpful in returning default values when data is not available.
  • Mostly used in Stream.generate() and similar factory-style methods.

• Syntax :

  public interface Supplier
  {
      T get();
      //no other abstract methods
  }

Programs:

• 1. Simple program without lambda expression:

  import java.util.function.Supplier;
  
  public class MainApp
  {
      public static void main(String[] args)
      {
          // Supplier to provide a random number using anonymous class
          Supplier<Double> randomNumber = new Supplier<Double>() {
              @Override
              public Double get() {
                  return Math.random();
              }
          };
  
          // Get numbers
          System.out.println("Random Number 1 : " + randomNumber.get());
          System.out.println("Random Number 2 : " + randomNumber.get());
      }
  }

  Output:

  Random Number 1 : 0.456739283
  Random Number 2 : 0.928374652

  (Output will vary every time since Math.random() generates random values)

• 2. Program with lambda expression:

  import java.util.function.Supplier;
  
  public class MainApp
  {
      public static void main(String[] args)
      {
          // Supplier to provide a random number using lambda expression
          Supplier<Double> randomNumber = () -> Math.random();
  
          // Get numbers
          System.out.println("Random Number 1 : " + randomNumber.get());
          System.out.println("Random Number 2 : " + randomNumber.get());
      }
  }

  Output:

  Random Number 1 : 0.456739283
  Random Number 2 : 0.928374652

  (Output will vary every time since Math.random() generates random values)