An application is a typical Java program (client-side or server-side) consisting of a set of related classes, with each one usually being coded in a separate file. Classes can be grouped into packages and arranged in a hierarchical directory structure on disk. (This hierarchical structure is independent of the object hierarchy based on inheritance.) As in C++, one file includes a main() function, allowing it to be invoked on the command-line and making it an entry-point for the application.

Here is some sample Java code, containing a class for printing the current date and time:

package examples.times; // the package this class is made part of

import java.util.Date; // import a class from the core Java API

public class CurrentTime
{
    private String currentTime; // member variable, illustrative

    // constructor
    public CurrentTime() {
        String time = getTimeAsString();
        System.out.println("The date/time is " + time);
        this.currentTime = time; // illustrative, not used
    }

    // method to get a String representation of the current time
    public String getTimeAsString() {
        Date now = new java.util.Date();
        return now.toString();
    }
 
    // main: automatically executed on calling 
    // "java examples.times.CurrentTime" from the command-line 
    public static void main(String args[])
    {
        new CurrentTime(); // call the constructor
    }
}

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