What is an API

Question

Hi,
I feel a little ashamed to ask this question. But after a lot of efforts I have not been able to understand what is an API.
Also I have heard about the jakarta apache api. When exaclty do we use the jakarta apache api.
As far as I know for developing the java programs you need to install the jdk and that is sufficien to compile your programs. Then wherw do the api exactly fit in.
if you are using servlets then you use eclipse with a webserver like tomcat. Do people call eclipse an api.
Please clear my doubt.
prashant

Answer 1

An API is the stuff, i.e. the methods, that are provided by a piece of software so that you can use them in your programs to manipulate the software.
apache's API: apache is a program that is widely used to return web pages to browsers that request them. If apache provides methods that can be called from a computer program that you write, then apache provides an API, or an "interface", so that your program can interact with and manipulate the apache program.
As far as I know for developing the java programs you need to install the jdk and that is sufficien to compile your programs. Then where do the api exactly fit in.
java's API is all the stuff that you can use in your java programs. If it helps, think of the java-byte-code-maker as a piece of software. Your goal is to make that software produce byte code that does what you want it to, e.g. write to a file. So, you have to manipulate that software somehow. The java classes and methods in the java docs are the API that allow you to manipulate the java-byte-code-maker.
if you are using servlets then you use eclipseI've programmed servlets before, and I've never used eclipse.
a webserver like tomcat
Tomcat is a piece of software. Tomcat provides classes and methods that allow you to interact with and manipulate the Tomcat software to perform certain tasks. Those methods and classes are the Tomcat API.
Do people call eclipse an api
Eclipse is a piece of software. If Eclipse provides classes and methods that allow you to write a program and interact with the Eclipse software, then those classes and methods are an API.
For comparison, here is a piece of software that provides no API:
public class Test
  public static void main(String args[])
    System.out.println("hello world");
}That software does not provide any way for a program that you write to interact with it. You could write a program that causes the software to execute and provide some command line arguments, and those command line arguments will get stored in the args variable, but the program ignores the args variable.