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‎.gitignore‎

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target/
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**/*.iml
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*.iml
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.attached_pid*
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.idea/

‎README.md‎

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# Validation
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A simple and easy-to-use validation utility library.
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By Tom Ansill
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## Motivation
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I got tired of manually including null checks, empty array checks, and various kinds of checks against bad input parameters.
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So I decided to build a library to make things a bit easier for me.
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### Why not use `Objects.requireNonNull(T)`?
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`Objects.requireNonNull(T)` will throw `NullPointerException` and I disagree with this choice of exception because `NullPointerException` is supposed to be thrown in event of null object being de-referenced. Like:
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```
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StringBuilder sb = null;
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sb.append("something"); // <-- This will throw NullPointerException because you are trying to de-reference a null object
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```
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So, hence the name `NullPointerException`, you get the exception because you are attempting to de-reference a null value and it blows up on you.
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I don't believe this is the case here where I want to ensure that parameters that are passed in is not null. I'm not necessarily trying to dereference it.
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I think `IllegalArgumentException` is more appropriate exception to best describe the problem.
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## Prerequisites
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* Java 8 or better
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* Maven
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## Download
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**No Maven Repository available yet ):**
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For now, you need to build and install it on your machine.
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```bash
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$ git clone https://github.com/tomansill/java-validation
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$ cd java-validation
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$ mvn install
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```
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Then include the dependency in your project's `pom.xml`:
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```xml
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<dependency>
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<groupId>com.ansill.validation</groupId>
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<artifactId>validation</artifactId>
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<version>0.1.0</version>
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</dependency>
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```
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## How to use
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### Null Checks
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Use `Validation.assertNonnull(Object)` to assert that object is not null:
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```java
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import com.ansill.validation.Validation;
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public class Application{
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public static void main(String[] args){
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String message = null;
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Application application = new Application();
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application.print(message);
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}
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public void print(String message){
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Validation.assertNonnull(message);
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System.out.println(message);
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}
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}
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```
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When you run the code, it will yield this message:
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```
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Exception in thread "main" java.lang.IllegalArgumentException: Value is expected to be non-null but is found to be null
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at Application.print(Application.java:10)
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at Application.main(Application.java:7)
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```
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### Natural Number Checks
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Use `Validation.assertNaturalNumber(long)` to assert that number is a natural number (no negative number or zero):
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```java
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import com.ansill.validation.Validation;
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public class Application{
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public static void main(String[] args){
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Application application = new Application();
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application.setPort(0);
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}
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private int port = 80;
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public void setPort(int port){
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Validation.assertNaturalNumber(port, "port");
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this.port = port;
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}
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}
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```
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When you run the code, it will yield this message:
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```
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Exception in thread "main" java.lang.IllegalArgumentException: Value in variable 'port' is expected to be a natural number (1, 2, ..., N-1, N) but it is actually not a natural number
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at Application.setPort(Application.java:10)
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at Application.main(Application.java:6)
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```
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### Non-Negative Checks
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Use `Validation.assertNonnegative(long)` to assert that number is a positive number:
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```java
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import com.ansill.validation.Validation;
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public class Application{
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public static void main(String[] args){
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Application application = new Application();
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application.add((short) 0, -1);
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}
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public void add(short one, long two){
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Validation.assertNonnegative(one);
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Validation.assertNonnegative(two);
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System.out.println(one + two);
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}
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}
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```
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When you run the code, it will yield this message:
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```
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Exception in thread "main" java.lang.IllegalArgumentException: Value is expected to be non-negative but value is actually a negative number
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at Application.add(Application.java:10)
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at Application.main(Application.java:6)
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```
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### Non-Empty String Checks
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Use `Validation.assertNonemptyString(String)` to assert that String is non-empty:
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```java
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import com.ansill.validation.Validation;
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public class Application{
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public static void main(String[] args){
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Application application = new Application("");
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}
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public final String name;
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public Application(String name){
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Validation.assertNonemptyString(name, "name");
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this.name = name;
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}
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}
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```
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When you run the code, it will yield this message:
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```
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Exception in thread "main" java.lang.IllegalArgumentException: Value in variable 'name' is expected to be non-empty but value is actually a empty string
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at Application.<init>(Application.java:9)
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at Application.main(Application.java:5)
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```
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### Non-Empty Array/Collection
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Use `Validation.assertNonempty(Object[])` or `Validation.assertNonempty(Collection)` to assert that Array/Collection is non-empty:
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```java
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import com.ansill.validation.Validation;
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import java.util.*;
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public class Application{
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public static void main(String[] args){
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Application application = new Application(Collections.emptyList());
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}
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public final Collection hostnames;
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public Application(Collection hostnames){
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Validation.assertNonempty(hostnames);
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this.hostnames = hostnames;
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}
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}
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```
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When you run the code, it will yield this message:
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```
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Exception in thread "main" java.lang.IllegalArgumentException: Value is expected to be non-empty but value is actually empty
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at Application.<init>(Application.java:11)
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at Application.main(Application.java:7)
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```
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### Array/Collection Member Null Check
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Use `Validation.assertNonnullElements(Object[])` or `Validation.assertNonnullElements(Collection)` to assert that Array/Collection does not have null elements:
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```java
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import com.ansill.validation.Validation;
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import java.util.*;
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public class Application{
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public static void main(String[] args){
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Application application = new Application(Arrays.asList("google.com", null, "github.com", null, null, "reddit.com"));
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}
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public final Collection hostnames;
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public Application(Collection hostnames){
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Validation.assertNonnullElements(hostnames, false);
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this.hostnames = hostnames;
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}
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}
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```
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When you run the code, it will yield this message:
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```
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Exception in thread "main" java.lang.IllegalArgumentException: Value is expected to have all of its list members to be non-null but the list contains null members. Invalid members are located at indices [1, 3, 4]
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at Application.<init>(Application.java:11)
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at Application.main(Application.java:7)
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```

‎pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xmlns="http://maven.apache.org/POM/4.0.0"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>com.ansill.validation</groupId>
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<artifactId>validation</artifactId>
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<version>0.1.0</version>
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<packaging>jar</packaging>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<configuration>
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<source>8</source>
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<target>8</target>
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</configuration>
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</plugin>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-surefire-plugin</artifactId>
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<version>2.22.1</version>
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</plugin>
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</plugins>
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</build>
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<properties>
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<junit.jupiter.version>5.4.2</junit.jupiter.version>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
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</properties>
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<dependencies>
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<dependency>
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<groupId>com.google.code.findbugs</groupId>
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<artifactId>jsr305</artifactId>
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<version>3.0.0</version>
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</dependency>
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<dependency>
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<groupId>org.junit.jupiter</groupId>
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<artifactId>junit-jupiter-api</artifactId>
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<version>${junit.jupiter.version}</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.junit.jupiter</groupId>
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<artifactId>junit-jupiter-engine</artifactId>
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<version>${junit.jupiter.version}</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.junit.jupiter</groupId>
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<artifactId>junit-jupiter-params</artifactId>
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<version>5.4.2</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>com.google.code.gson</groupId>
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<artifactId>gson</artifactId>
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<version>2.8.5</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

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