> For the complete documentation index, see [llms.txt](https://lin-4.gitbook.io/cs-notebook/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://lin-4.gitbook.io/cs-notebook/some-notes.md).

# some notes

## 1.

### import java.util.EventListener;

public interface ActionLister extends EventListener{

public void actionPerformed(ActionEvent e);

}

The ActionListener example is an interface with only one method. With Java SE 8, an interface that follows this pattern is known as a "functional interface". **Note:** This type of interface, was previously known as a Single Abstract Method type(SAM).

**Using functional interfaces with anonymous inner classes are a common pattern in Java**. In addition to the EventListener classes, interfaces like Runnable and Comparator are used in a similar manner.

## **2 type signature**

In [computer science](https://en.wikipedia.org/wiki/Computer_science) , a **type signature** or **type annotation** defines the inputs and outputs for a [function](https://en.wikipedia.org/wiki/Function_\(computer_science\)) , [subroutine](https://en.wikipedia.org/wiki/Subroutine) or [method](https://en.wikipedia.org/wiki/Method_\(computer_science\)). A type signature includes the number of arguments, the types of arguments and the order of the arguments contained by a function. A type signature is typically used during overload resolution for choosing the correct definition of a function to be called among many overloaded forms.

## **3.method signature**

In the [Java programming language](https://en.wikipedia.org/wiki/Java_\(programming_language\)) , a method signature is the method name and the number and type of its parameters. Return types and thrown exceptions are not considered to be a part of the method signature.

## 4. Built-in Class

These classes are not really part of the language; they are provide in the package *java.lang*.

eg:

String, Object, Boolean, Integer, Double, etc

## 7. typeless language VS type language

## 8. functional programming language

C++, JavaScript are called functional programming language because we can write functions and use them when required. Some of these languages support Object Oriented Programming as well as Functional programming.