Guava Magic: ArrayListMultimap

import com.google.common.collect.ArrayListMultimap;

public class TestGuavaMultiMaps {

  public static void main(String[] args) {

    ArrayListMultimap<String, String> multimap = ArrayListMultimap.create();

    multimap.put("A", "1");

    multimap.put("B", "1");

    multimap.put("C", "1");

    multimap.put("A", "2");

    multimap.put("B", "2");

    multimap.put("C", "2");

    multimap.put("A", "3");

    multimap.put("B", "3");

    System.out.println(multimap); // {A=[1, 2, 3], B=[1, 2, 3], C=[1, 2]}

    multimap.asMap().remove("A");

    System.out.println(multimap); // {B=[1, 2, 3], C=[1, 2]}

    multimap.get("B").remove("1");

    System.out.println(multimap); // {B=[2, 3], C=[1, 2]}

    multimap.get("B").remove("2");

    multimap.get("B").remove("3");

    System.out.println(multimap); // {C=[1, 2]}

  }

}

How JMockit mocks static methods?

Dependency:
* Using old version

    <!-- jmockit should be before Junit -->
    <dependency>
      <groupId>com.googlecode.jmockit</groupId>
      <artifactId>jmockit</artifactId>
      <version>1.7</version>
    </dependency>

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
    </dependency>

Code:

import mockit.Mocked;
import mockit.NonStrictExpectations;
import org.junit.Before;
import org.junit.Test;

import static mockit.Deencapsulation.invoke;
import static org.junit.Assert.assertEquals;

public class JMockitStaticMethod {

  @Mocked({"getenv"})
  private System system;

  @Before
  public void init()
  {
    // allow to return mock value any number of times
    new NonStrictExpectations(system)
    {
      {
        invoke(System.class, "getenv", "MOCKED_VALUE");
        returns("MOCKED");
      }
    };
  }

  @Test
  public void testJMockitStatic() {
    assertEquals("MOCKED", System.getenv("MOCKED_VALUE"));
  }

}

Dependency:
* Using new version:

  <!-- jmockit should be before Junit -->
    <dependency>
      <groupId>org.jmockit</groupId>
      <artifactId>jmockit</artifactId>
      <version>1.23</version>
    </dependency>

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
    </dependency>


Code (mocks easier):

import mockit.Expectations;

import org.junit.Before;
import org.junit.Test;

import static mockit.Deencapsulation.invoke;
import static org.junit.Assert.assertEquals;

public class JMockitStaticMethod {


  @Before
  public void init()
  {
    new Expectations(System.class)
    {
      {
        invoke(System.class, "getenv", "MOCKED_VALUE");
// returns("MOCKED")
        result = new ClassCastException();
      }
    };
  }

  @Test(expected = ClassCastException.class)
  public void testJMockitStatic() {
    assertEquals("MOCKED", System.getenv("MOCKED_VALUE"));
  }

}

How to add jar into classpath at runtime?

  // pathToJar -> /path/to/jar/MyJarName.jar

  public void addToClassPath(String pathToJar) throws Exception {
    File file = new File(pathToJar);
    Method method = URLClassLoader.class.getDeclaredMethod("addURL", URL.class);
    method.setAccessible(true);
    method.invoke(ClassLoader.getSystemClassLoader(), file.toURI().toURL());
  }

TemporaryFolder in Junit

Dependencies:

    <dependency>

      <groupId>com.google.guava</groupId>

      <artifactId>guava</artifactId>

      <version>19.0</version>

    </dependency>

    <dependency>

      <groupId>junit</groupId>

      <artifactId>junit</artifactId>

      <version>4.12</version>

    </dependency>

Code:

import com.google.common.base.Charsets;

import com.google.common.io.Files;

import org.junit.Rule;

import org.junit.Test;

import org.junit.rules.TemporaryFolder;

import java.io.File;

public class TestTempFolder {

  // create temporary folder using Junit, it will be deleted automatically upon test success or failure

  // restriction: cannot be static

 // should be public

  @Rule

  public TemporaryFolder testFolder = new TemporaryFolder();

  @Test

  public void testTempFolder() throws Exception {

    // create file inside of temporary folder

    File mainFile = testFolder.newFile("main.csv");

    // write data into newly created file using guava lib

    Files.write("main data", mainFile, Charsets.UTF_8);

    // create folder inside of temporary folder

    File nestedFolder = testFolder.newFolder("nested");

    // create file inside of nested folder

    File nestedFile = new File(nestedFolder, "nested.csv");

    // write data into newly created file using guava lib

    Files.write("nested data", nestedFile, Charsets.UTF_8);

  }

}

3 ways to get file name without extension

Using apache commons

import org.apache.commons.io.FilenameUtils;

String fileNameWithoutExt = FilenameUtils.getBaseName(fileName);

                           OR

String fileNameWithOutExt = FilenameUtils.removeExtension(fileName);

Using Google Guava (If u already using it)

import com.google.common.io.Files;
String fileNameWithOutExt = Files.getNameWithoutExtension(fileName);

Or using Core Java

String fileName = file.getName();
int pos = fileName.lastIndexOf(".");
if (pos > 0) {
    fileName = fileName.substring(0, pos);
}