The Java tutorial Java 101: Classes and objects in Java introduces the fundamentals of Java classes and objects, including how to declare classes, describe attributes via fields, describe ...

JDO instance First-class objects Second-class objects JDO instance A JDO instance is a Java class instance that implements the application functions and represents data in an enterprise data store.

Single quotes are only used for single characters, such as ‘A’ or ‘9’. These are considered char values in Java, not strings. Have fun working with the System object and printing data to the console ...