SecurityManager in Java is to check whether the application codes can access some restricted resource such as file, socket etc. This can be used in applications which have high security requirements. With this feature turned on, our system resources can be secured with only permitted operations.When JVM starts, it will first check whether the SecurityManager is on by checking the system property java.security.manager, if it's on, then an instance of SecurityManager will be created and it can be used to check different permissions. By default the security manager is off, but there are a few way...