JAVA 8 LAMBDA BOOK

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If you're a developer with core Java SE skills, this hands-on book takes you through the language changes in Java 8 triggered by the addition of lambda. Java 8 Lambdas book. Read 20 reviews from the world's largest community for readers. If you're an experienced Java programmer, Java 8 Lambdas shows you . O'Reilly books may be downloadd for educational, business, or sales Media, Inc. Java 8 Lambdas, the image of a lesser spotted eagle, and.


Java 8 Lambda Book

Author:TEGAN LAPALME
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Pages:320
Published (Last):05.06.2016
ISBN:465-5-54662-619-7
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Java 8 Lambdas Richard Warburton Download Full High Quality Version for Free Where those designations appear in this book, and O'Reilly Media, Inc. was. There are many blogs and books about Java8. I find this tutorial very useful for beginners: * Java 8 Features Tutorial – The ULTIMATE Guide. Introduction. This book is not the first book about Java 8 lambda expressions and streams, and it's definitely not the last book about lambda expressions and.

Lambda expressions have a very simple syntax to write. Formal parameter list has no type declaration, so the type of list is implicitly inferred by compiler.

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Lambda expression in line 3 has two formal parameters, so parentheses around parameters list are required. Lambda expression in line 5 has explicit type for formal parameters x and y. Lambda expression in line 7 has no formal parameters. In this case, parentheses are required. Lambda expression starts from line 9 is a complicated example with three formal parameters and multiple lines of code in body.

In this case, braces are required to wrap the body. If a value is returned, the type of return value must be compatible with target type.

Lambda expression uses a very simple approach to handle resolution of names in the body. Listing 2. From code examples in Listing 2. To capture variables from enclosing context in lambda expression body, the variables must be final or effectively final.

Code in Listing 2. Method references are references to existing methods by name. For example, Object:: Object class. Method references can be used to remove more boilerplate code.

If the body of a lambda expression only contains one line of code to invoke a method, it can be replaced with a method reference.

StringProducer in Listing 2. In run method, method reference this:: Invoking run method will output text like StringProducerMain 65ab to the console. Using this:: The introduction of default methods is trying to solve a longstanding problem in Java interface design: All implementations must be updated to implement the new method.

This means interface design has to be done correctly at the first time and cannot happen iteratively without breaking existing code. Before Java 8, an interface can only have abstract methods. Abstract methods must be implemented by implementation classes. Default methods of interfaces in Java 8 can have both declarations and implementations.

If we want to add a new method to an existing interface, this new method can have default implementation. New code can override this default implementation to provide a better solution. The scenario is to insert records into a database. In the first version, interface RecordInserter only has one abstract method insert. SimpleRecordInserter class in Listing 2. Then we find out that the performance of inserting a lot of records is not very good, so we want to add batch inserting to improve performance.

So a new method insertBatch is added to the RecordInserter interface with default implementation. This default implementation can make sure SimpleRecordInserter class still works. To improve the performance, a new implementation FastRecordInserter class overrides the default implementation of insertBatch method and create a better solution.

In Java 8, interfaces can also have static methods. Helper methods related to an interface can be added as static methods, see Listing 2. Null reference is considered as The billion dollar mistake by its inventor Tony Hoare.

Maybe null should not be introduced into Java language in the first place. Suppose we have a method with argument val of a non-primitive type, we should check first to make sure the value of val is not null. Listing 5. If a method accepts multiple arguments, all these arguments should be checked.

Utility methods like Objects. Another case is for long object references, e. Groovy has safe navigation operator?. The idea behind Optional is quite simple. An Optional object is a holder of the actual object which may be null. Client code interacts with the Optional object instead of the actual object. The Optional object can be queried about the existence of the actual object.

Although the actual object may be null , there is always an Optional object. The major benefit of using Optional is to force client code to deal with the situation that the actual object that it wants to use may be null. Instead of using the object reference directly, the Optional object needs to be queried first. Optional objects are very easy to create. If you pass a null value to Optional. The simple usage of Optional is to query it first, then retrieve the actual object hold by it.

We can use boolean isPresent method to check if an Optional object holds a non-null object, then use T get method to get the actual value. But the code in Listing is still long and tedious.

Since Optional s are commonly used with if.. This other object acts as the default or fallback value. Optional provides some methods to use it in a functional way.

Code in Listing 2. For example, Object::toString references toString method of java. Object class. Method references can be used to remove more boilerplate code.

If the body of a lambda expression only contains one line of code to invoke a method, it can be replaced with a method reference. StringProducer in Listing 2. In run method, method reference this::toString is used to create an instance of StringProducer.

Invoking run method will output text like StringProducerMain 65ab to the console. Static method Refer to a static method using ClassName::methodName, e. String::format, Integer::max.

Instance method of a particular object Refer to an instance method of a particular object using instanceRef::methodName, e.

In Listing 2. Instance method of an arbitrary object of a particular type Refer to an instance method of any object of a particular type using ClassName::methodName, e. The syntax is the same as referring a static method. Class constructor Refer to a class constructor using ClassName::new, e. Array constructor Refer to an array constructor using TypeName[]::new, e.

All implementations must be updated to implement the new method.

This means interface design has to be done correctly at the first time and cannot happen iteratively without breaking existing code. Before Java 8, an interface can only have abstract methods. Abstract methods must be implemented by implementation classes.

Default methods of interfaces in Java 8 can have both declarations and implementations. If we want to add a new method to an existing interface, this new method can have default implementation. New code can override this default implementation to provide a better solution. The scenario is to insert records into a database. SimpleRecordInserter class in Listing 2.

So a new method insertBatch is added to the RecordInserter interface with default implementation. This default implementation can make sure SimpleRecordInserter class still works.

Table of Contents

Helper methods related to an interface can be added as static methods, see Listing 2. Null reference is considered as The billion dollar mistake by its inventor Tony Hoare.

Maybe null should not be introduced into Java language in the first place. Suppose we have a method with argument val of a non-primitive type, we should check first to make sure the value of val is not null. Listing 5. If a method accepts multiple arguments, all these arguments should be checked. Utility methods like Objects. Another case is for long object references, e. Groovy has safe navigation operator?. The idea behind Optional is quite simple. An Optional object is a holder of the actual object which may be null.

Client code interacts with the Optional object instead of the actual object.

Best Java 8 Books

The Optional object can be queried about the existence of the actual object. Although the actual object may be null, there is always an Optional object. The major benefit of using Optional is to force client code to deal with the situation that the actual object that it wants to use may be null. Instead of using the object reference directly, the Optional object needs to be queried first.

Optional objects are very easy to create.

5 Good Books to Learn Java 8 Functional Programming

We can use boolean isPresent method to check if an Optional object holds a non-null object, then use T get method to get the actual value.Sign in Sign up. This interface has a single method, actionPerformed, which is called by the button instance when a user actually clicks the on-screen button.

Lambda Expressions. Feb 06, Wangyiran rated it really liked it. In run method, method reference this::toString is used to create an instance of StringProducer.

One of the good book I read on java 8.

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