SpringBoot application failing to start with error: Failed to bind properties under 'server.port' to java.lang.Integer

I have tried to change the default port in my SpringBoot application from 8080 to 8888 by adding the server.port property to my SpringBoot's application.properrties file.
After the change, I am seeing the following exception while starting

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( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
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 :: Spring Boot ::        (v2.1.6.RELEASE)

2019-07-04 23:29:17.980  INFO 4925 --- [           main] com.oc.springsample.Start                : Starting Start on MacBook-Pro-6.local with PID 4925 (/springsample/target/classes started by foo in /springsample)
2019-07-04 23:29:17.983  INFO 4925 --- [           main] com.oc.springsample.Start                : No active profile set, falling back to default profiles: default
2019-07-04 23:29:18.560  WARN 4925 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'tomcatServletWebServerFactory' defined in class path resource [org/springframework/boot/autoconfigure/web/servlet/ServletWebServerFactoryConfiguration$EmbeddedTomcat.class]: Initialization of bean failed; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'servletWebServerFactoryCustomizer' defined in class path resource [org/springframework/boot/autoconfigure/web/servlet/ServletWebServerFactoryAutoConfiguration.class]: Unsatisfied dependency expressed through method 'servletWebServerFactoryCustomizer' parameter 0; nested exception is org.springframework.boot.context.properties.ConfigurationPropertiesBindException: Error creating bean with name 'server-org.springframework.boot.autoconfigure.web.ServerProperties': Could not bind properties to 'ServerProperties' : prefix=server, ignoreInvalidFields=false, ignoreUnknownFields=true; nested exception is org.springframework.boot.context.properties.bind.BindException: Failed to bind properties under 'server.port' to java.lang.Integer
2019-07-04 23:29:18.568  INFO 4925 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2019-07-04 23:29:18.571 ERROR 4925 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

Failed to bind properties under 'server.port' to java.lang.Integer:

    Property: server.port
    Value: 8888 // comments
    Origin: class path resource [application.properties]:1:15
    Reason: failed to convert java.lang.String to java.lang.Integer

Action:

Update your application's configuration

Following is the content in my application.properties file

server.port = 8888 // changed port to 8888