Blog

About Frameworks, Algorithms and Software Engineering

Mai 4, 2018

Regular Expressions in Java

I used Java regular expressions (java.util.regex) for years uncritically. University taught me that regular expression are efficient.

Some day in my project I had the challenge to search a large amount of words (>1.000) in a large number of documents (>10.000). I remembered college and instead of searching each word in each document. I decided to search in each document for the regular expression <Word1>|<Word2>|...|<Word1000>. That should have been far more efficient than searching each word in each document … However, regular expression is not regular expression and the fast automatons known to me from college are not the same that are provided by Java.

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Apr 2, 2018

Exact String Matching in Practice

Initially I was interested in string search from an academic view point - just understand the algorithm and be able to implement it. After this passion culminated in the project (StringSearchAlgorithms), I began to compare it to others …

It became obvious that many algorithms worked in theory, but were slow or even failing in practice. Actually most academic algoirthms on string search are optimized for a certain situation dependent on:

  • processors
  • encoding
  • programming languages and APIs

The following sections describe the challenges string search is confronted to in practice.

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Mai 29, 2017

Testrecorder – Next Steps

After Presenting at Karlsruher Entwicklertag it is time to write a few words about the future of Testrecorder … Testrecorder is a Java tool vor recording runtime situations. Recording means, that we intercept method invocation and capture the state before and after the invocation. From this captured state we generate JUnit-tests.

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Okt 12, 2016

Naming of Interfaces and Implementations

Which is your naming convention for implementation classes? Do your prefer FormDataValueImpl or IFormDataValue ?

Intrinsically I should be pleased about this question - at least someone seems to care about naming conventions … but sorry, both conventions are little more than crap. Unfortunately these patterns are very popular, so my criticism will have little effect. Here you are:

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Aug 10, 2016

String Search in Java (using the JDK-API)

String search is a common problem, appearing every time we check that a string is contained in another. The JDK Standard API provides some basic functionality for this, yet there are more efficient algorithms for larger patterns and larger texts.

In this posting I present an overview over the string searching features of the Java API, starting with a short definition of string searching and ending with an overview of libraries that provide more features for string searching (more details will follow in later postings).

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Mai 21, 2016

Accessing Private Fields and Methods with XRayInterface

This posting is about accessing private fields and methods, by adopting a foreign interface to a given java class (not already implementing the given interface). Why? Yet, in my former posting about Repairing Legacy Code I mentioned the challenge of accessing hidden state (private fields) before and after method invocations.

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Mär 27, 2016

Repairing Legacy Code - Automatically

Many Projects already use automated regression testing. Unfortunately we cannot rely on this in situations that afford them most, for maintaining foreign (untested) legacy code. Here I do not only wish for automated regression tests, I also wish for automated test generators. Why does such a tool not exist?

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Java Forum Stuttgart 2018

Meet me at Java Forum Stuttgart. This is (primarily) not a talk about Testrecorder, Urs Metz and myself present some Java tools that can generate complete JUnit test suites.

Entwicklertag 2018

Meet me at Entwicklertag 2018. Urs Metz and myself will present an overview of tools for automatic generation of tests.

Meine Projekte

I host some Open Source Projects on Github, my most successful projects have their own website: