Error: Could not find or load main class

package com.demo.journalApp;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.mongodb.MongoDatabaseFactory;
import org.springframework.data.mongodb.MongoTransactionManager;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@SpringBootApplication
@EnableTransactionManagement
@Configuration
@EnableAutoConfiguration
public class JournalApplication {

    public static void main(String[] args) {
        SpringApplication.run(JournalApplication.class, args);
    }

    @Bean
    PlatformTransactionManager add(MongoDatabaseFactory db) {
        return new MongoTransactionManager(db);
    }

}