In the MVC model, the controller receives the request from the user, processes the request, builds the data for the view (model), and selects the view to return the result to the user. In this tutorial, we will look at an overview about the controller… Read More
The Spring Boot Dashboard is a function of the Spring Tool Suite which allows us to manage all applications that use Spring Boot in our workspace. Using the Spring Boot Dashboard, in addition to starting and stopping one or more Spring Boot applications, it also… Read More
Using the Cloud Foundry CLI can help us talk directly to Cloud Foundry Providers like Pivotal Cloud Foundry. In this tutorial, I will show you how to use the Cloud Foundry CLI to login into Pivotal Cloud Foundry and view the information which we want.… Read More
In my previous tutorial, I showed you how to convert Java object to JSON using the Jackson library. So what if we wanted to do the reverse, ie converting JSON to Java object? In this tutorial, we will learn more about that. As an example,… Read More
Jackson is a standard library for handling JSON-related issues in Java. In this tutorial, we will learn how to convert Java objects to JSON using the Jackson library. First, I will illustrate with a Maven project as follows: Jackson dependency is as follows:
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<dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.18.1</version> </dependency> |
The… Read More
As you all know, the Optional object is a generic object, its data type can be any object, and therefore, we can meet the case that its data type is also an Optional object, such as: Optional<Optional<String>>. To resolve this problem, Java introduces us to… Read More
This method will check whether an Optional object is not empty? If this object is empty, it returns false. For example:
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package com.huongdanjava.javaexample; import java.util.Optional; public class Example { public static void main(String[] args) { String s = new String("Khanh"); Optional<String> opt = Optional.ofNullable(s); System.out.println(opt.isPresent()); } } |
Result:
This method first will check whether our Optional object is empty or not? If not empty, convert its value to another value. Similar to the filter() method, this method returns an Optional object with a value after conversion. For example:
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package com.huongdanjava.javaexample; import java.util.Optional; public class Example { public static void main(String[] args) { String s = new String("Khanh"); Optional<String> opt = Optional.ofNullable(s); opt.map(x -> x.toLowerCase()) .filter(x -> x.contains("k")) .ifPresent(x -> System.out.println("Name: " + x)); } } |
In the above example,… Read More
This method first will check whether our Optional object is empty or not? If not, then continue to check whether its value meets a certain condition or not? If satisfied, it returns an Optional object containing this value, otherwise returns an empty Optional object. For… Read More
This method was introduced from Java 9. This method is similar to the ifPresent() method which I introduced in this tutorial, but here is a difference since we have one more Runnable parameter, so that in-case if the Optional object is empty, the object of the… Read More
