重学java（二）

Code reuse is one of the most important factors in software development. It is a very good idea to put frequently-used functions together and build a library for yourself. Whenever some method is used, just simply make a method invocation.

For Java, it’s straightforward to manage such a library. Here a simple example in Eclipse.

The library will contain only one “add” method.

Step 1: Create a “Java Project” named as “MyMath”, and a simple “add” method under “Simple” class.

Package structure is as follows:

Simple.java

public class Simple { public static int add(int a, int b){ return a+b; } }

Step 2: Export as a .jar file.

Right Click the project and select “export”, a window is show as follows.

Following the wizard, to get the .jar file.

Step 3: Use the jar file.

Right click the target project, and select “Build Path”->”Add External Archives”->following wizard to add the jar file.

Now you can make a simple method call.

public class Main { public static void main(String[] args) { System.out.println(Simple.add(1, 2)); } }