Huong Dan Java - Page 70 of 75 - Java development tutorials

Cleanup resource automatically with Project Lombok

When we use a resource like InputStream, OutputStream in Java, we should remember to close that resource after using. Before Java 7, we can close a resource in a finally block as below:

package com.huongdanjava.lombok;

import java.io.*;

public class Example {

    public static void main(String[] args) throws IOException {
        InputStream is = null;
        try {
            is = new FileInputStream(new File("/Users/Khanh/text.txt"));
        } finally {
            if (is != null) {
                is.close();
            }
        }
    }
}

package com.huongdanjava.lombok;

import java.io.*;

public class Example {

public static void main(String[] args) throws IOException {

InputStream is = null;

try {

is = new FileInputStream(new File("/Users/Khanh/text.txt"));

} finally {

if (is != null) {

is.close();

}

Since Java 7, we can use the try with resource to… Read More

Logging with Project Lombok

7 years ago by Khanh NguyenLombok

Normally, when we use a Logging framework like Log4J, Logback or Simple Logging Facade for Java (SLF4J) for these Logging frameworks in a class, we need declare for example as below:

package com.huongdanjava.lombok;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Example {

    public static final Logger LOGGER = LoggerFactory.getLogger(Example.class);

    public void print(String message) {
        LOGGER.info(message);
    }
}

package com.huongdanjava.lombok;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

public class Example {

public static final Logger LOGGER = LoggerFactory.getLogger(Example.class);

public void print(String message) {

LOGGER.info(message);

}

But with Project Lombok, we don’t need to do that. When using Project… Read More

Builder Pattern with Project Lombok

7 years ago by Khanh NguyenLombok

Normally, when we need to create an object with a lot of its information, we can use the Builder Pattern for that purpose. For example, I have a Student class as below:

package com.huongdanjava.lombok;

public class Student {

    private String firstName;
    private String middleName;
    private String lastName;
    private String country;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getMiddleName() {
        return middleName;
    }

    public void setMiddleName(String middleName) {
        this.middleName = middleName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }

    @Override
    public String toString() {
        return "Student{" +
                "firstName='" + firstName + '\'' +
                ", middleName='" + middleName + '\'' +
                ", lastName='" + lastName + '\'' +
                ", country='" + country + '\'' +
                '}';
    }
}

package com.huongdanjava.lombok;

public class Student {

private String firstName;

private String middleName;

private String lastName;

private String country;

public String getFirstName() {

return firstName;

}

public void setFirstName(String firstName) {

this.firstName = firstName;

}

public String getMiddleName() {

return middleName;

}

public void setMiddleName(String middleName) {

this.middleName = middleName;

}

public String getLastName() {

return lastName;

}

public void setLastName(String lastName) {

this.lastName = lastName;

}

public String getCountry() {

return country;

}

public void setCountry(String country) {

this.country = country;

}

@Override

public String toString() {

return "Student{" +

"firstName='" + firstName + '\'' +

", middleName='" + middleName + '\'' +

", lastName='" + lastName + '\'' +

", country='" + country + '\'' +

'}';

}

To build this object with all information using the Builder Pattern, we… Read More

toString(), equals() and hashCode() method with Project Lombok

7 years ago by Khanh NguyenLombok

In many situations working with Java object, we need define toString(), equals() or hashCode() method. These methods can be added to the Java object automatically by using Project Lombok. In this tutorial, I will show you all about this! First of all, we need a… Read More

Getter, Setter and Constructors with Project Lombok

7 years ago by Khanh NguyenLombok

In this tutorial, I will show you how we can use Project Lombok to generate Getter, Setter methods or the constructors in a Java object automatically. OK, first of all, we need to create an example Maven project. with Project Lombok dependency as below:

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.24</version>
    <scope>provided</scope>
</dependency>

<groupId>org.projectlombok</groupId>

<artifactId>lombok</artifactId>

<scope>provided</scope>

</dependency>

Install Project Lombok plugin into IntelliJ IDEA on macOS

7 years ago by Khanh NguyenLombok

In this tutorial, I will show you how we can install Project Lombok plugin into IntelliJ IDEA on macOS. – First of all, we need open our IntelliJ IDEA. – Go to IntelliJ IDEA -> Preferences… and then Plugins – Press Browse repositories… to search… Read More

Using flatMap() method of Stream object in Java

7 years ago by Khanh NguyenJava Basic

When working with Stream in Java, sometime we can have a Stream with datatype of a List, Set or Array of object. For example:

List<String> students1 = new ArrayList<>();
students1.add("Khanh");

List<String> students2 = new ArrayList<>();
students2.add("Thanh");
students2.add("Dung");

List<List<String>> students = Arrays.asList(students1, students2);

Stream<List<String>> stream = students.stream();

List<String> students1 = new ArrayList<>();

students1.add("Khanh");

List<String> students2 = new ArrayList<>();

students2.add("Thanh");

students2.add("Dung");

List<List<String>> students = Arrays.asList(students1, students2);

Stream<List<String>> stream = students.stream();

Here, we have List of List of String object and when convert into Stream object, we have Stream of List… Read More

Filter a Map using Stream and Lambda Expression in Java

7 years ago by Khanh NguyenJava Basic

To filter a Map using Stream and Lambda Expression in Java, we will use the filter() method of Stream object which will be retrieved from Entry object of Map object with Lambda Expression as filter a List. How is it in details? Let learn together in… Read More

Sort a Map using Stream and Collectors in Java

7 years ago by Khanh NguyenJava Basic

In this tutorial, I will show you how to order elements in a Map object using the Stream object and the Collectors object in Java by key and by value. For example, we have a Map object like this:

Map<String, Integer> studentMap = new HashMap<>();
studentMap.put("Khanh", 31);
studentMap.put("Thanh", 25);
studentMap.put("Dung", 35);

Map<String, Integer> studentMap = new HashMap<>();

studentMap.put("Khanh", 31);

studentMap.put("Thanh", 25);

studentMap.put("Dung", 35);

Prior to Java 8, to… Read More

Documenting your RESTful API with Springfox for Swagger in Spring Boot

7 years ago by Khanh NguyenSpring Boot

Like RAML, the Swagger specification, or OpenAPI specification, is a specification used to define RESTful Web Service APIs. Springfox is a library used to create the RESTful API documentation in Spring, implement the Swagger specification. In this tutorial, let’s find out how to create RESTful… Read More