Re Usable Code

[Justin Char]

I hear everyone talk about Java reusable code.

I always right my programs from scratch.

How do I use pieces of other programs that are not related to the current one I am writing. I use Eclipse. How would I call like Sql connection from a previous program so I don't have to re-write the connection string in my current program I am writing. I am just curious how this is done.

Thank You

[Steve Luke]

Generally the reusable portions of your code are packed into JARs and the JARs are placed in your classpath. You then can import any of the classes in the JAR into your application.

When using an IDE you normally have to configure the classpath differently than you do for command-line tools. So look up Eclipse's documentation to see how to add a JAR (or an external project) to a Project's class path.

[Ilja Preuss]

Another way to do it inside Eclipse is to have one or more projects with reusable code, and put those on the build path of your application projects.

[fred rosenberger]

think about the java API. There is tons of code there that can be used by anyone, at any time. Basically, you write a class that has the methods you want, compile it, then call them like the Math class or the String class methods.

[Justin Char]

So if I understand this correctly.

I would build a jar or a class and put it in my class path.

Once in my classpath (java build path same)

I would just reference it like a method

So if I called it Justin.java or jar
[code]
private void Justin(String string) {
}
[code/]
Say it was a SQL connection string. Then my password and login would be hidden. Just by entering this method I would connect to the database?

[fred rosenberger]

not exactly...

to use a Math class method, you have to explicitly tell it the class and method:

   double v = Math.sin(3.1415);

if your methods are static, you would have to do the same thing:

   double v = Justin.method1(3.1415);

if the methods aren't static, like for a String, you need to make the object, and then call the methods on the object:

   String v = new String("hello");
   int k = v.indexOf('e');

or

   Justin v = new Justin("hello");
   int k = v.justingsMethod("db2");

[Justin Char]

Justin v = new Justin("hello");
int k = v.justingsMethod("db2");

So if my connection String is called

FINAL db = new FINAL();
 db.dbConnect(
"   connection      string   "

public String FINAL;
Justin db = new Justin("DB");
int FINAL = db.justindbMethod("db");

This should then call the connection string from the class I added to the classpath?