Convert Java 8 Streams to Collections

Process data using Java 8 Streams and store in Collections including List, Set or Map.

“If we knew what it was we were doing, it would not be called research, would it?”
― Albert Einstein

1. Introduction

Java 8 Streams provide a cool facility to combine several operations in a single statement and express it concisely. Once the data is processed, you can collect the data in a List (or another collection). In this article, we present several methods to collect the results of these stream operations into collections.

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Using a Java TreeSet

Covers the basic operations on a java TreeSet including creation, iteration, finding elements, etc.

The unexamined life is not worth living.
― Socrates

1. Introduction

A java Set is a Collection containing only unique elements. A TreeSet is an implementation of the Set which uses a Red-Black tree implementation. In this article, we demonstrate how to properly create and use a TreeSet.

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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.

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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.

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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.

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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.

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Java – Pivot Table using Streams

Implement a Pivot Table in Java using Java 8 Streams and Collections.

“Money may not buy happiness, but I’d rather cry in a Jaguar than on a bus.”
― Françoise Sagan

1. Introduction

Today let us see how we can implement a pivot table using java 8 streams. Raw data by itself does not deliver much insight to humans. We need some kind of data aggregation to discern patterns in raw data. A pivot table is one such instrument. Other more visual methods of aggregation include graphs and charts.

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Java Streams groupingBy Examples

Learn how to perform SQL-like grouping and summarizing calculations on Java Collections (List, Map, etc).

1. Introduction

Have you wanted to perform SQL-like operations on data in a List or a Map? Maybe computing a sum or average? Or perhaps performing an aggregate operation such as summing a group? Well, with Java 8 streams operations, you are covered for some of these.

A previous article covered sums and averages on the whole data set. In this article, we show how to use Collectors.groupingBy() to perform SQL-like grouping on tabular data.

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Using Java Collectors

Use Java 8 Streams and Collectors to slice and dice lists including computing sums, averages, partitioning and more.

1. Introduction

Java 8 provides the new Streams facility which makes many Collection operations easy. Streaming items from a collector and filtering the data are trivial. As well as are sorting, searching and computing aggregates. That is, if you are familiar with the many Collectors functions available. We present some of these functions here.

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Java ArrayList Benchmark

Learn about ArrayList and LinkedList performance. In this article, we test creation, addition and iteration performance of these containers.

“Don’t mistake activity with achievement.”
― John Wooden

1. Introduction

Let us examine the performance characteristics of List Implementations – ArrayList and LinkedList. We perform the testing for a variety of list sizes from 100 items to 1M items. We use the JMH test harness to conduct the test on a single core machine. Results are presented below.

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