How to get streaming results with Spring JPA, Java 8 Stream and PostgreSQL | Spring Boot

In tradition approach, implementing Data Access Layer makes lots of boilerplate code. Spring Data provides us Spring JPA which supports the ways to write interface for repositories and custom finder methods. The implementation will be done automatically by Spring Framework.

The tutorial shows you how to make streaming results with Spring JPA, Java 8 Stream and PostgreSQL using Spring Boot.

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@DataJPATest with Spring Boot

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Java 8 – How to convert List to Map & Map to List

In the tutorial, JavaSampleApproach will guide you How to convert List to Map (Map to List) with Java 8.

Related Posts:
1. Java 8 – Lambda Expressions
2. Java 8 – Functional Interfaces
3. Java 8 – Method References

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How to use Java 8 Encode (Decode) an Image to Base64

For some purpose like transfering an image through RestfulAPI or saving an image to a DataBase, We need Encoder (Decode) the image to Base64. In the tutorial, JavaSampleApproach will guide you how to use Java 8 for converting.

Related post: Java 8 Base64

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Java 8 Base64

Java 8 Base64 provides a standard way to do Base64 encoding and decoding.
There are three types of Base64 encoding:
Basic: Encoder produces a set of characters within A-Za-z0-9+/. Decoder rejects any character NOT mapped to A-Za-z0-9+/.
URL: Encoder produces a URL or safe filename which is set of characters within A-Za-z0-9+_.
MIME: Output is mapped to MIME friendly format.

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Java 8 Multiple CompletableFutures

In previous posts, we have concept of how to use CompletableFutures. This tutorial is about combining multiple CompletableFutures, it is one of the most important and useful abilities of Java 8 asynchronous processing.

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Java 8 CompletableFutures

Java 8 multithreading programming has an important feature named CompletableFuture.
In previous post about Java Future, we have the concept of a Future object, which can help us make something done while waiting for other things. However, although we can inspect Future objects to see if they’re done, what if we wanna execute some code whenever its ready? We still have to wait until the result is available.

CompletableFuture meets the requirement, and more than that.

Related articles:
Java Future
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Java 8 Multiple CompletableFutures

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Java 8 – Method References

Method References make it clear when referring to the existing method by name.

In the article Lambda Expressions and Functional Interfaces, we use lambda expressions to create anonymous methods and sometimes, calling an existing method is the only thing it does.

When using lambda expression without input arguments or those input arguments doesn’t make sense, we can use Method References to simplify the syntax.

This tutorial introduces four kinds of Method References and how to use them efficiently with some Functional Interfaces.

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Java 8 – Functional Interfaces

Functional Interfaces is one of the new important things of Java 8. In previous article, we had a little view about common use cases of Lambda Expression including Runnable and ActionListener. They are example of Functional Interfaces.

This tutorial helps you have deeper concept of Functional Interface, then some interfaces which are provided in java.util.function package such as Predicate and Function.

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