Some basic questions - Java

[Fusion]

Hello! I'm new to Java, so I thought I might receive some help here.

I saw this code before, but without any explanation;

public interface Printable {

	public abstract void print();

}

Could someone just kindly explain what it does?

My second questions is related to this code;

public class SystemException extends Exception {

	private String context;

	public SystemException(String message) {

		super(message);
	}

	public SystemException(String message, String context) {

		super(message);
		this.context = context;
	}

	public String getContext() {

		return context;

	}

Quite frankly, I don't exactly understand what SystemException does, especially in this context. I would really appreciate some help to understand these. Also, please do excuse me if I have done something wrong when writing the codes in here. :)

[KevinWorkman]

The problem with both of these code snippets is that they don't really *do* anything by themselves.

Your first snippet is simply an interface. Anything that implements your Printable interface must also define a print() function. That's it. More info here: What Is an Interface? (The Java™ Tutorials > Learning the Java Language > Object-Oriented Programming Concepts)

You second snippet is an Exception, but you haven't posted any code that uses it. More info here: Lesson: Exceptions (The Java™ Tutorials > Essential Classes)

[Fusion]

Thank you very much for you help, KevinWorkMan! In the case of Printable and implement, could you pleasehelp me with this certain code with an explanation of what this code exactly does;

public abstract class Figure implements Printable{

	public void print() {

		System.out.println(getType() + " Area = " + getArea());

	}

	public abstract Double getArea();

	protected String getType() {

		return "Square";

[KevinWorkman]

Again, the code doesn't actually *do* anything, as it doesn't have a main() method. What you've posted is a class that implements Printable, which just means that it must have a print() function. Did you read the tutorial on interfaces I posted?

[Fusion]

Again, the code doesn't actually *do* anything, as it doesn't have a main() method. What you've posted is a class that implements Printable, which just means that it must have a print() function. Did you read the tutorial on interfaces I posted?

Yes, just read it and I feel I understand more now. Thank you very much!