Java Basic Archives - Page 2 of 12

Run a simple web server with Java using jwebserver

We often use the Java server runtime to run Java web applications such as Tomcat, Jetty, … From Java version 18, by default, Java also supports us to run a server runtime using the jwebserver command. By default, the jwebserver command will run a web… Read More

Get the application version information from the META-INF/MANIFEST.MF file inside the jar file

2 years ago by Khanh NguyenJava Basic

A need that we often meet is how to know what version of the application we are running, so we can know what features the application is supporting up to this version. In Java, depending on what application you are using, Web application or Desktop… Read More

Introduction about Java Module System

2 years ago by Khanh NguyenJava Basic

Java Module System was introduced by Java from Java 9 to solve some problems of Java that if you notice you will see how its necessary? NoClassDefFoundError: This error occurs while our Java program is running. The JVM cannot find the class needed to execute… Read More

Nested class in Java

3 years ago by Khanh NguyenJava Basic

Java allows us to define a class that belongs to another class, for example:

package com.huongdanjava.javaexample;

public class Application {

    class Builder {

    }
}

package com.huongdanjava.javaexample;

public class Application {

class Builder {

}

Class is defined inside another class, we call it nested class and this other class is called outer class. In my example above, the Builder is a nested class and… Read More

instanceof operator in Java

3 years ago by Khanh NguyenJava Basic

The instanceof operator in Java is an operator used to check if this object is an instance of a certain class or interface or not? The return result of this operator will be true if the object is an instance of the class you are… Read More

Introduce about text block in Java

4 years ago by Khanh NguyenJava Basic

Previously, when declaring a multi-line text in Java, for example:

Welcome to Huong Dan Java 
My name is Khanh

1 2	Welcome to Huong Dan Java My name is Khanh

We will usually declare the following:

String text = "Welcome to Huong Dan Java \n" + 
    "My name is Khanh";

1 2	String text = "Welcome to Huong Dan Java \n" + "My name is Khanh";

Result: But from Java 13 onwards, you do not need to declare so anymore. Java now supports the text blocks with the ability to declare multiple lines… Read More

Install Java JDK

4 years ago by Khanh NguyenJava Basic

To work with the Java programming language, the first thing you need to do is set up the environment to run the application with the Java JDK. In this article, I will guide you through the steps to install Java JDK! To install Java JDK,… Read More

Introduction about Bean Validation in Java

4 years ago by Khanh NguyenJava Basic

In the tutorial about @Entity and @Table annotation in JPA, I mentioned to you the concept of Java Bean, they are POJOs with at least one constructor with no parameters. We often use Java Bean to contain information of an object. To ensure that the… Read More

Switch statement in Java

4 years ago by Khanh NguyenJava Basic

Switch statement in Java is a statement used to check the value of a variable, which can have different values, depending on the value of this variable we can define a different set of statements. For example, I have n variable that can be valued… Read More

Use Lambda Expression to sort elements of a List in Java

5 years ago by Khanh NguyenJava Basic

Normally, before Java 8, when we want to sort the elements of a List in Java, we will use the Comparator object. Eg:

package com.huongdanjava.javaexample;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class Example {

	public static void main(String[] args) {
		List<String> names = new ArrayList<>();
		names.add("Thanh");
		names.add("Khanh");
		names.add("Tan");

		Collections.sort(names, new Comparator<String>() {
		    @Override
		    public int compare(String s1, String s2) {
		        return s1.compareTo(s2);
		    }
		});

		for (String s : names) {
			System.out.println(s);
		}
	}
}

package com.huongdanjava.javaexample;

import java.util.ArrayList;

import java.util.Collections;

import java.util.Comparator;

import java.util.List;

public class Example {

public static void main(String[] args) {

List<String> names = new ArrayList<>();

names.add("Thanh");

names.add("Khanh");

names.add("Tan");

Collections.sort(names, new Comparator<String>() {

@Override

public int compare(String s1, String s2) {

return s1.compareTo(s2);

}

});

for (String s : names) {

System.out.println(s);

}

Result: From Java 8 onwards, we have another way of doing this. That is, using the sort() method of the List… Read More

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