Symmetric-Key Cryptography is an encryption system in which the same key is used for the encoding and decoding of the data. The safe distribution of the key is one of the drawbacks of this method, but what it lacks in security it gains in time complexity. One should always assume that the encryption algorithms are […]
SecureRandom class in Java provides a cryptographically secure pseudo – random number generator and its intended use is for security sensitive applications. In this example, we will not use it for its intended purpose, but rather present its methods in a simple password generator. 1.Password Generator Using Secure Random A convention, we made for our […]
Java examples to check if an Array (String or Primitive type) contains a certain values, updated with Java 8 stream APIs. 1. String Arrays 1.1 Check if a String Array contains a certain value “A”. StringArrayExample1.java package com.mkyong.core; import java.util.Arrays; import java.util.List; public class StringArrayExample1 { public static void main(String[] args) { String[] alphabet = […]
Code snippets to convert a primitive array int[] to a List<Integer> : int[] number = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; List<Integer> list = new ArrayList<>(); for (int i : number) { list.add(i); } In Java 8, you can use the Stream APIs to do the boxing and conversion like this […]
In the ConfigServer Security & Firewall (CSF) configuration file, update the CT_LIMIT value to limit the number of connections per IP address. This is a simple trick to prevent some types of Denial of Service (DOS) attack. Note To stop the Denial of Service (DoS) attack immediately, read this null route example. 1. /etc/csf/csf.conf SSH […]
A collection of Java date and time examples. 1. Java Date Time APIs In old days, we use the following classic Date and Calendar APIs to represent and manipulate date. java.util.Date – date and time, print with default time-zone. java.util.Calendar – date and time, more methods to manipulate date. java.text.SimpleDateFormat – formatting (date -> text), […]
In Java 8, you can use the predefined java.time.temporal.TemporalAdjusters to adjust a date or Temporal 1. TemporalAdjusters Example to move a date to firstDayOfMonth, firstDayOfNextMonth, next Monday and etc. TestDate.java package com.mkyong.time; import java.time.DayOfWeek; import java.time.LocalDate; import java.time.temporal.TemporalAdjusters; public class TestDate { public static void main(String[] args) { LocalDate localDate = LocalDate.now(); System.out.println("current date : […]
This article shows you how to add days to the current date, using the classic java.util.Calendar and the new Java 8 date and time APIs. 1. Calendar.add Example to add 1 year, 1 month, 1 day, 1 hour, 1 minute and 1 second to the current date. DateExample.java package com.mkyong.time; import java.text.DateFormat; import java.text.SimpleDateFormat; import […]
Few examples to show you how to use Java 8 Duration, Period and ChronoUnit objects to find out the difference between dates. Duration – Measures time in seconds and nanoseconds. Period – Measures time in years, months and days. 1. Duration Example A java.time.Duration example to find out difference seconds between two LocalDateTime DurationExample.java package […]
Few examples to show you how to format java.time.LocalDateTime in Java 8. 1. LocalDateTime + DateTimeFormatter To format a LocalDateTime object, uses DateTimeFormatter TestDate1.java package com.mkyong.time; import java.time.LocalDateTime; import java.time.format.DateTimeFormatter; public class TestDate1 { public static void main(String[] args) { //Get current date time LocalDateTime now = LocalDateTime.now(); System.out.println("Before : " + now); DateTimeFormatter formatter […]
In Java, you can use the Jackson library to convert a Java object into a Map easily. 1. Get Jackson pom.xml <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.6.3</version> </dependency> 2. Convert Object to Map 2.1 A Jackson 2 example to convert a Student object into a java.util.Map Student.java package com.mkyong.examples; import java.util.List; public class Student { private String […]
Few build.gradle examples to show you how to create multiple start scripts or executable Java application. 1. Single Start Script 1.1 In Gradle, you can use the application plugin to create an executable Java application : build.gradle apply plugin: ‘application’ mainClassName = "com.mkyong.analyzer.run.threads.MainRunApp" applicationName = ‘mainApp’ applicationDefaultJvmArgs = ["-Xms512m", "-Xmx1024m"] 1.2 Create the executable Java […]
The static keyword in Java is a modifier used to create memory efficient code. It helps in managing the memory occupied by objects, variables and method definitions. The static keyword makes sure that there is only one instance of the concerned method, object or variable created in memory. It is used when one needs to […]
In Java, there is no ready make API to compare two java.util.Set 1. Solution Here’s my implementation, combine check size + containsAll : SetUtils.java package com.mkyong.core.utils; import java.util.Set; public class SetUtils { public static boolean equals(Set<?> set1, Set<?> set2){ if(set1 == null || set2 ==null){ return false; } if(set1.size()!=set2.size()){ return false; } return set1.containsAll(set2); } […]
While saving an object containing the new Java 8 java.time.LocalDateTime, the following error is thrown : org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [java.time.LocalDateTime] to type [java.util.Date] Tested Spring 4.3.2.RELEASE Spring Data MongoDB 1.9.2.RELEASE Is Spring-data supporting the new Java 8 Date APIs (JSR-310)? 1. Spring Data + JSR-310 Yes, Spring-data supports the […]
Ramadan is the 9th month of the Islamic calendar, the entire month. 1. HijrahDate -> Ramadan 2016 Full example to calculate the start and end of the Ramadan 2016 TestHijrahDate.java package com.mkyong.date; import java.time.LocalDate; import java.time.chrono.HijrahDate; import java.time.temporal.ChronoField; import java.time.temporal.TemporalAdjusters; public class TestDate { public static void main(String[] args) { //first day of Ramadan, 9th […]
This MinguoDate calendar system is primarily used in Taiwan (Republic of China…) (ISO) 1912-01-01 = 1-01-01 (Minguo ROC) To convert the current date to the Minguo date, just subtracts the current year with number 1911, for example 2016 (ISO) – 1911 = 105 (Minguo ROC) 1. LocalDate -> MinguoDate Review a full example to convert […]
The java.util.ResourceBundle is a library used for internationalization (multiple languages). It is able to return messages as per the default Locale configured for the system. Such a functionality is used when one develops systems to be used all over the world. 1. How it works? The library reads a property file based on the locale and name […]
Few Java 8 java.time.ZonedDateTime examples to show you how to convert a time zone between different countries. Table of contents 1. Convert LocalDateTime to ZonedDateTime 2. Malaysia (UTC+08:00) -> Japan (UTC+09:00) 3. France, Paris (UTC+02:00, DST) -> (UTC-05:00) 4. References 1. Convert LocalDateTime to ZonedDateTime The LocalDateTime has no time zone; to convert the LocalDateTime […]
Here is the code to convert java.util.Date to java.time.LocalDate. Date date = new Date(); LocalDate localDate = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDate(); // different way of create instant object LocalDate localDate = Instant.ofEpochMilli(date.getTime()).atZone(ZoneId.systemDefault()).toLocalDate(); Convert java.util.Date to java.time.LocalDateTime. Date date = new Date(); LocalDateTime localDateTime = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime(); Convert java.util.Date to java.time.ZonedDateTime. Date date = new Date(); ZonedDateTime zonedDateTime = date.toInstant().atZone(ZoneId.systemDefault()); […]
Java 8 examples to show you how to convert from Instant to ZonedDateTime 1. Instant -> ZonedDateTime Example to convert a Instant UTC+0 to a Japan ZonedDateTime UTC+9 InstantZonedDateTime1.java package com.mkyong.date; import java.time.Instant; import java.time.ZoneId; import java.time.ZonedDateTime; public class InstantZonedDateTime1 { public static void main(String[] argv) { // Z = UTC+0 Instant instant = Instant.now(); […]
Java 8 examples to show you how to convert from Instant to LocalDateTime 1. Instant -> LocalDateTime The java.time.LocalDateTime has no concept of time zone, just provide a zero offset UTC+0. InstantExample1.java package com.mkyong.date; import java.time.Instant; import java.time.LocalDateTime; import java.time.ZoneOffset; public class InstantExample1 { public static void main(String[] argv) { // Parse a ISO 8601 […]
A Java 8 example to display all the ZoneId and its OffSet hours and minutes. P.S Tested with Java 8 and 12 1. Display ZoneId and Offset DisplayZoneAndOffSet.java package com.mkyong; import java.time.LocalDateTime; import java.time.ZoneId; import java.time.ZoneOffset; import java.time.ZonedDateTime; import java.util.HashMap; import java.util.LinkedHashMap; import java.util.Map; public class DisplayZoneAndOffSet { public static final boolean SORT_BY_REGION = false; […]
Here are a few Java examples of converting a String to the new Java 8 Date API – java.time.LocalDate DateTimeFormatter formatter = DateTimeFormatter.ofPattern("d/MM/yyyy"); String date = "16/08/2016"; //convert String to LocalDate LocalDate localDate = LocalDate.parse(date, formatter); The key is understand the DateTimeFormatter patterns Note You may interest at this classic java.util.Date example – How to […]
Java 8 Stream examples to sort a Map, by keys or by values. 1. Quick Explanation Steps to sort a Map in Java 8. Convert a Map into a Stream Sort it Collect and return a new LinkedHashMap (keep the order) Map result = map.entrySet().stream() .sorted(Map.Entry.comparingByKey()) .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (oldValue, newValue) -> oldValue, LinkedHashMap::new)); P.S By […]
A Java 8 example to show you how to convert a Stream to a List via Collectors.toList Java8Example1.java package com.mkyong.java8; import java.util.List; import java.util.stream.Collectors; import java.util.stream.Stream; public class Java8Example1 { public static void main(String[] args) { Stream<String> language = Stream.of("java", "python", "node"); //Convert a Stream to List List<String> result = language.collect(Collectors.toList()); result.forEach(System.out::println); } } output […]
Review a Stream containing null values. Java8Examples.java package com.mkyong.java8; import java.util.List; import java.util.stream.Collectors; import java.util.stream.Stream; public class Java8Examples { public static void main(String[] args) { Stream<String> language = Stream.of("java", "python", "node", null, "ruby", null, "php"); List<String> result = language.collect(Collectors.toList()); result.forEach(System.out::println); } } output java python node null //
Few Java examples to convert a Map to a List Map<String, String> map = new HashMap<>(); // Convert all Map keys to a List List<String> result = new ArrayList(map.keySet()); // Convert all Map values to a List List<String> result2 = new ArrayList(map.values()); // Java 8, Convert all Map keys to a List List<String> result3 = […]
This tutorial will show you how to back up and restore (import or export) MySQL / MariaDB database or tables. Table of contents: 1. MySQL – Backup or export databases and tables 2. MySQL – Restore or import databases and tables 3. Backup and Restore MySQL 4. References 1. MySQL – Backup or export databases […]
Final keyword in Java is a modifier used to restrict the user from doing unwanted code or preventing from the code or value from being changed. It is possible to use this keyword in 3 contexts. They are: Final keyword as a variable modifier Final keyword as a method modifier Final keyword as a class […]
In this tutorial, we will show you how to install Oracle JDK 8 On CentOS. Environment : CentOS 6.8 Oracle JDK 8u102 Note This guide should work on Fedora and RedHat. 1. Get Oracle JDK 8 1.1 Visit Oracle JDK download page, look for RPM version. 1.2 Copy the download link of jdk-8u102-linux-x64.rpm and wget […]
In simple, mocking is creating objects that mimic the behavior of real objects. Refer to the following case study : Tested : Java 1.8 JUnit 4.12 Mockito 2.0.73-beta Mock Object Read this Wikipedia Mock object. 1. Java Examples A simple Author and Book example. 1.1 BookService to return a list of books by author name. […]
In this tutorial, we will show you how to test the Spring DI components with JUnit frameworks. Technologies used : JUnit 4.12 Hamcrest 1.3 Spring 4.3.0.RELEASE Maven 1. Project Dependencies To integrate Spring with JUnit, you need spring-test.jar pom.xml <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> <scope>test</scope> <exclusions> <exclusion> <groupId>org.hamcrest</groupId> <artifactId>hamcrest-core</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.hamcrest</groupId> <artifactId>hamcrest-library</artifactId> <version>1.3</version> […]
In JUnit, you can organize the test cases into different categories, and run those categorized test cases with @Categories.ExcludeCategory or @Categories.IncludeCategory Note This @Categories annotation is available since JUnit 4.12 1. Category = Marker Interface In JUnit, you need to create marker interfaces to represent the categories: PerformanceTests.java package com.mkyong.category; //category marker interface public interface […]
Includes hamcrest-library and test the class property and its value with hasProperty() : P.S Tested with JUnit 4.12 and hamcrest-library 1.3 ClassPropertyTest.java package com.mkyong; import org.junit.Test; import java.util.Arrays; import java.util.List; import static org.hamcrest.CoreMatchers.is; import static org.hamcrest.Matchers.containsInAnyOrder; import static org.hamcrest.Matchers.hasProperty; import static org.junit.Assert.assertThat; public class ClassPropertyTest { //Single Object @Test public void testClassProperty() { Book obj […]
In Java, there are two types of exceptions – checked and unchecked exception. Here’s the summary : Checked – Extends java.lang.Exception, for recoverable condition, try-catch the exception explicitly, compile error. Unchecked – Extends java.lang.RuntimeException, for unrecoverable condition, like programming errors, no need try-catch, runtime error. 1. Custom Checked Exception Note Some popular checked exception : […]
In JUnit, you can use @FixMethodOrder(MethodSorters.NAME_ASCENDING) to run the test methods by method name, in lexicographic order. P.S Tested with JUnit 4.12 ExecutionOrderTest.java package com.mkyong; import org.junit.FixMethodOrder; import org.junit.Test; import org.junit.runners.MethodSorters; import static org.hamcrest.CoreMatchers.is; import static org.junit.Assert.assertThat; //Sorts by method name @FixMethodOrder(MethodSorters.NAME_ASCENDING) public class ExecutionOrderTest { @Test public void testB() { assertThat(1 + 1, is(2)); […]
The Infinitest is a continuous testing plugin, it helps to run the test automatically. 1. Install on IntelliJ 1.1 In Plugins, clicks on the “Browse repositories…” 1.2 Type “Infinitest” and clicks on the “Install” button. 1.3 Restart the Intellij IDEA. 2. Add Infinitest facet In the project structure / settings, add a “Infinitest” facet. 3. […]
By default, Intellij IDEA doesn’t compile classes automatically. But, you can enable the auto compile feature by following steps : In “Project settings or preferences” Select “Build, Execution, Deployment -> Compiler” Checked Make project automatically P.S This feature is available since IDEA 12 References Brand New Compiler Mode in IntelliJ IDEA 12
Forget about JUnit assertEquals(), to test a Map, uses the more expressive IsMapContaining class from hamcrest-library.jar pom.xml <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> <scope>test</scope> <exclusions> <exclusion> <groupId>org.hamcrest</groupId> <artifactId>hamcrest-core</artifactId> </exclusion> </exclusions> </dependency> <!– This will get hamcrest-core automatically –> <dependency> <groupId>org.hamcrest</groupId> <artifactId>hamcrest-library</artifactId> <version>1.3</version> <scope>test</scope> </dependency> </dependencies> 1. IsMapContaining Examples All the below assertThat checks will be passed. […]
