Implement retry handler for a task in Java

Implement an utility class such that, it takes a code snippet and executes with the configured number of retries until it is successful.

 

Find the below working application.

 

RetryableTask.java

package com.sample.app.interfaces;

public interface RetryableTask {  
    /**
     * Block of code to retry
     */
    void execute();
}

RetryHandler.java

package com.sample.app.handler;

import com.sample.app.interfaces.RetryableTask;

public class RetryHandler {
  private int noOfRetries = 0;

  public RetryHandler(int noOfRetries) {
    if (noOfRetries <= 0) {
      throw new IllegalArgumentException("Number of retries is <= 0");
    }

    this.noOfRetries = noOfRetries;
  }

  public void execute(RetryableTask retryableTask) {
    int retries = 0;
    while (true) {
      try {
        retryableTask.execute();
        break;
      } catch (Throwable t) {
        retries++;
        if (retries > this.noOfRetries) {
          System.err.println("Maximum retries finished......");
          throw t;
        }
        System.err.println("Error occurred, retrying another time");
      }
    }
  }

}

RetryTaskDemo.java

package com.sample.app;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import com.sample.app.handler.RetryHandler;
import com.sample.app.interfaces.RetryableTask;

public class RetryTaskDemo {

  public static void main(String[] args) {
    RetryableTask task = new RetryableTask() {

      @Override
      public void execute() {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String input;
        System.out.println("Enter 'p' to exit successfully, non 'p' to throw an exception");
        try {
          input = br.readLine();
          if ("p".equals(input)) {
            System.out.println("Task executed successfully");
          } else {
            throw new RuntimeException("Task failed");
          }
        } catch (IOException e) {
          e.printStackTrace(System.err);
        }

      }
    };
    
    RetryHandler retryHandler = new RetryHandler(2);
    retryHandler.execute(task);
  }

}

Sample run 1 : Successful scenario

Enter 'p' to exit successfully, non 'p' to throw an exception
p
Task executed successfully

Sample run 2 : Failed scenario

Enter 'p' to exit successfully, non 'p' to throw an exception
p
Task executed successfully

Sample run 2 : Failed scenario
Enter 'p' to exit successfully, non 'p' to throw an exception
f
Error occurred, retrying another time
Enter 'p' to exit successfully, non 'p' to throw an exception
f
Error occurred, retrying another time
Enter 'p' to exit successfully, non 'p' to throw an exception
f
Maximum retries finished......
Exception in thread "main" java.lang.RuntimeException: Task failed
  at com.sample.app.RetryTaskDemo$1.execute(RetryTaskDemo.java:25)
  at com.sample.app.handler.RetryHandler.execute(RetryHandler.java:20)
  at com.sample.app.RetryTaskDemo.main(RetryTaskDemo.java:35)

Sample run 3 : Task successful in given number of retries

Enter 'p' to exit successfully, non 'p' to throw an exception
f
Error occurred, retrying another time
Enter 'p' to exit successfully, non 'p' to throw an exception
f
Error occurred, retrying another time
Enter 'p' to exit successfully, non 'p' to throw an exception
p
Task executed successfully

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