Removing Items in a Loop from a List

Learn about several methods to remove items in a loop from a java collection.

“Puns are the highest form of literature.”
― Alfred Hitchcock

1. Introduction

When you have a List or a Set or any other Collection, you may sometimes need to remove items in a loop. For example, you may be maintaining a list of messages for processing, and need to occasionally purge stale items from the list. In such a scenario, you would loop around the collection and remove the stale items.

Continue reading “Removing Items in a Loop from a List”

Use Java8 Optional to Avoid Problems

Use Java 8 Optional to avoid unexpected conditions like NPE in your code.

“Life always begins with one step outside of your comfort zone.”
― Shannon L. Alder

1. Introduction

Java version 1.8 provides the new class Optional which represents an abstration of an optional value. That is the object may contain a value or a null. This class provides several useful features which help java programmers avoid NullPointerException. Let us look into this class in more detail.

Continue reading “Use Java8 Optional to Avoid Problems”

Using Java ArrayList’s List Iterator

A ListIterator allows traversal of a Java ArrayList in forward or backward direction.

“A man devoid of hope and conscious of being so has ceased to belong to the future.”
― Albert Camus, The Myth of Sisyphus and Other Essays

1. Introduction

Java’s ArrayList class provides a list iterator which allows, among other things, traversal of the list in either direction. This is in comparison to a normal Iterator that allows traversal of the list in forward direction only. In this article, we delve into the usage and behavior of the ListIterator when used with an ArrayList.

Continue reading “Using Java ArrayList’s List Iterator”

Searching a List in Java

Easily search a java list using java 8 predicate functions.

“Make improvements, not excuses. Seek respect, not attention.”
― Roy T. Bennett, The Light in the Heart

1. Introduction

Searching, sorting and iterating are some of the fundamental operations required when using a list. Searching refers to finding one or more objects in the list that match a given condition. In this article, we look at some methods for searching a list in java.

Continue reading “Searching a List in Java”

Sorting Lists in Java

Learn how to sort a List in java. Use Java 8 Lambdas to compose sort conditions.

“You can only be afraid of what you think you know.”
― Jiddu Krishnamurti

1. Introduction

Sorting a list is a very common requirement when programming in java. Out of the box, java provides for sorting using a performant algorithm so there is no need to roll your own algo for the purpose. In this article, we demonstrate how to sort a list in java.

Continue reading “Sorting Lists in Java”

An Introduction to Python Sets

Python supports sets which are a collection of unique elements and provide operations for computing set union, intersection and difference.

“The world is a book and those who do not travel read only one page.”
― Augustine of Hippo

1. Introduction

A set is a collection of unique elements. A common use is to eliminate duplicate elements from a list. In addition, it supports set operations like union intersection and difference.

Continue reading “An Introduction to Python Sets”

Getting Started with Scrapy

Learn how to use Python Scrapy to Extract information from Websites.

“When life gives you lemons, chunk it right back.”
― Bill Watterson

1. Introduction

Scrapy is a python-based web crawler which can be used to extract information from websites. It is fast, simple and can navigate pages just like a browser can.

Continue reading “Getting Started with Scrapy”

Listing a Directory With Python

Learn how to list contents of a directory from python. Also, easily find and process files matching conditions from your python program.

“If at first you don’t succeed, destroy all evidence that you tried.”
― Steven Wright

1. Introduction

There are several methods to list a directory in python. In this article we present a few of these along with the caveats for each.

Continue reading “Listing a Directory With Python”

Regular Expressions Examples

Learn how to build regular expression patterns for parsing phone numbers, emails, etc.

. Introduction

Regular Expressions provide a powerful method to handle parsing tasks while handling texts. Whether the problem is a simple search for a pattern, or splitting a string into components, regular expressions are widely used today.

Continue reading “Regular Expressions Examples”