How to implement CompletableFuture class in java8?

     CompletableFuture deals with asynchronous programming. It run the process asynchronously. It allows the programs to execute in parallelly.

Built in package: java.util.concurrent.

Why completableFuture class?

CompletableFuture is efficient and provide response in timely manner. It has many functions listed below.

• supplyAsync ,runAsync : It deals with asynchronous computations to run the tasks.
• thenApply,thenAccept,thenRun : Multiple tasks executed and linked together to perform the computation.
• thenCombine,thenCompose,allOf : It combines the tasks.
• Exception handling: If any error occurs, this will handle.

Let the program begins.

First, Asynchronous Computation using completableFuture Program in java is given below.

Steps:

• ·       Create a public class CFEg with main() function.
• ·       Next, include the lambda expression to execute the code.
• ·       To print the output, use try and catch block to avoid errors.

//Program to implement Asynchronous computation using CompletableFuture.

import java.util.concurrent.*;

public class CFEg { 

  public static void main(String[] args) { 

              CompletableFuture<String> fu1 = CompletableFuture.supplyAsync(() -> {

        return "Hi,Asynchronous Computation is done with completableFuture";

              });

        try {

              System.out.println(fu1.get());

        } catch(Exception e)

        {

        System.out.println(e);

         }

}

}

Save,compile and execute the program to get the output.

C:\raji\blog>javac CFEg.java

C:\raji\blog>java CFEg

Hi,Asynchronous Computation is done with completableFuture

Next program is to implement the chaining tasks.

Program to implement chaining tasks using CompletableFuture:

Steps:

• ·       Create a class and main() function.
• ·       Create three objects for CompletabeFuture. Two for getting input as chaining tasks. Third one for combining these two.
• ·       Print the output using try and catch block.

//Program to implement chaining tasks using CompletableFuture:

import java.util.concurrent.*;

public class CFEg1 { 

public static void main(String[] args) { 

CompletableFuture<String> fut1 = CompletableFuture.supplyAsync(() -> "Welcome to the world of");

CompletableFuture<String> fut2 = CompletableFuture.supplyAsync(() -> "CompletableFuture coding");

CompletableFuture<String> combinedFuture = fut1.thenCombine(fut2, (ts1, ts2) -> ts1 + " " + ts2);

 try {

              System.out.println(combinedFuture.get());

        } catch(Exception e)

        {

        System.out.println(e);

         }

}

}

Compile and execute the program.

C:\raji\blog>javac CFEg1.java

C:\raji\blog>java CFEg1

Welcome to the world of CompletableFuture coding

Next program is given below.

Program to implement combining future using CompletableFuture:

Steps:

• ·       Import the built in package.
• ·       Create a class and include main function.
• ·       Using the system functions to print the output.

//Program to implement combining future using CompletableFuture:

import java.util.concurrent.*;

public class CFEg2 { 

  public static void main(String[] args) { 

try {

CompletableFuture<Void> fut = CompletableFuture.supplyAsync(() -> "Asynchronous")

   .thenAcceptAsync(res -> System.out.println(res + "  Programming"));

fut.get();

 } catch(Exception e)

        {

        System.out.println(e);

         }

}

}

Run the program and the output is displayed.

C:\raji\blog>javac CFEg2.java

C:\raji\blog>java CFEg2

Asynchronous  Programming

These are the different programs to implement CompletableFuture class in java8. It is useful in building efficient code.