Java beginners Guide

Byron KiourtzoglouMay 18th, 2010Last Updated: October 21st, 2012

2 300 1 minute read

First steps in Java programming.

For a introduction tutorial in Java please see the official help from SUN here
where, except of the core language, several technologies and APIs are
introduced. We propose to begin by reading the trails covering the
basics and continue with the rest of the tutorials.

We propose to :

Keep the code straightforward and easy to read
Split functionality in logical components (classes) that interconnect if necessary
Try to comply with code re-usability design patterns, where common functionality is implemented in a public accessed methods
Document your code, using Javadoc comments and/or simple comments
Use a logging framework (Apache log4j is widely deployed and used) to produce logs
Use a testing framework (JUnit is widely deployed and used) to test your code
If you code involves String manipulation (splitting, adding, scanning
characters etc), use the StringBuilder class rather than the String
class, the StringBuilder implementation is much faster
If your code involves lists or maps, the ArrayList and HashMap are the fastest
implementations, nevertheless if you are using the contains(Object)
method on a collection, then the HashSet is the fastest implementation
introducing a O(1) cost.
Java 5 and later versions include a management console (jconsole). You can use it to monitor your application
If your code involves pattern matching, prefer to use the Pattern and
Matcher classes, rather than the Pattern.matches(regex, input)
convenience method. Compile the pattern and use the Matcher.find()
method as described below, especially if you reuse the same pattern
where you should compile the pattern only once.

Preferred method for patter matching:

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main {

  public static void main(String args[]) throws Exception {

    Pattern p = Pattern.compile("Java \\d");
    String candidate = "this is a Java test";
    Matcher m = p.matcher(candidate);

    System.out.println("result=" + m.find());
  }
}