A Java 8 tutorial is essential for a developer who is new to the language. If you are unsure where to start, the Java Tech Network has many resources. For example, you can learn about the Streams API, Lambda expressions, Functional interfaces, and Concatenating strings with Streams.
Lambda expressions
Lambda expressions are particular types of variable expressions. They are used to express a single function or a group of parts. They use the name of the variable declared in the enclosing context to access its values. This helps simplify name resolution and scope. Lambda expressions can also access local variables.
Lambda expressions can be used to implement event listeners. They can also be used to express functions without using a method name. The examples in this Java 8 tutorial will demonstrate the different types of lambda expressions.
Functional interfaces
You have probably heard of the new functional interface in Java 8. These interfaces are similar to objects but have only one abstract method. In Java, you can passcode from one place to another using lambda expressions. You can also use lambda expressions instead of static methods.
You can use two interfaces to process data: a Consumer interface accepts one argument and has no return value, and a consumer interface accepts two arguments. It has the same properties as a Consumer interface but returns a deal instead.
Streams API
Java 8 introduced a new feature, the Streams API, which provides a sequence of values to be processed. Unlike regular lists and arrays, streams don’t store elements; instead, they consume from a source that provides the data. As a result, streams can perform SQL-like and everyday functional programming language operations.
Streams have various methods and properties, including filter() and map and reduce functions. They also have lazy evaluation and parallelism.
Concatenating strings with Streams
One of the most commonly used ways to concatenate strings in Java is using the StringBuilder class. While this method is convenient, it’s not recommended for multi-threaded applications. This is because StringBuilder objects are immutable, and you should avoid using them in loops.
When you want to concatenate multiple strings, you can use the StringJoiner class. It has a cleaner interface than StringBuilder, which requires logic to add commas before and after each element. StringJoiner is one of the hidden gems of Java SE 8. In addition, Java 8 features include lambda expressions, streams, and CompletableFuture.
Timezone offset
In this Java 8 tutorial, we’ll learn how to use the Timezone class to calculate the time difference between two places. Time zones are regions of the earth with the same standard time as UTC. A time zone ID is a string that begins with UTC, followed by a number, such as +09:00 for Europe/Copenhagen.
Time zone offset is a way to document how time changes across regions. For example, the offset of America/Los_Angeles is -08:00 during DST. You can ask for this offset using a method that takes the OffsetDateTime, which is then converted into the ZoneOffset.
Default methods in interfaces
Default methods in interfaces provide incremental functionality to a type without breaking the implementing classes. Because Java allows classes to implement multiple interfaces, a class can have several default methods. In such a case, the compiler will report the presence of duplicate default methods. These are used to define utility methods and provide a class’s default functionality.
A child class can override default methods in interfaces. This method is called the super method. In Java 8, a child class can extend another interface. However, the child interface will inherit the implementation of the default method.
Check exceptions
When dealing with arrays, it’s common to encounter an unchecked exception. This type of exception indicates that an index that does not exist is being accessed. For example, if you’re working with an array with ten items, an exception will occur when you try to access item 11.
A checked exception is a type of exception you can declare in a method declaration. If you don’t contain an exception, it won’t be caught by the calling code. Instead, it will bubble up to the main program loop. This is a violation of the principle of least surprise.
