java coverage is 0% with Junit & Jacoco from the command line

I used only 'command line' in all of these processes and I want to do that.(not using Ant, maven, gradle, etc.)

I would like to run Junit test case and JaCoCo coverage estimation.

First, below is my code

Calculator.java:

public class Calculator {
  public int evaluate(String expression) {

    int sum = 0;
    for(String summand: expression.split("\\+"))
        sum += Integer.valueOf(summand);
    System.out.println("Hello World!!");
    return sum;
  }
}

CalculatorTest.java:

import static org.junit.Assert.assertEquals;
import org.junit.Test;

public class CalculatorTest {
  @Test
  public void evaluatesExpression(){
    Calculator calculator = new Calculator();
    int sum = calculator.evaluate("1+2+3");
    assertEquals(6, sum);
  }
}

2 java files are in C\Cal and Cal folder contains 4 jar files (junit-4.12.jar, hamcrest-core-1.3.jar, jacococli.jar, jacocoagent.jar)

In this situation, I maked classfile Calculator.class.

javac Calculator.java

And then, I maked exec (I think it is execution file of jacoco) file to estimate unit-test coverage of Calculator.java file.

java -javaagent:jacocoagent.jar=destfile=jacoco.exec

After that, I extracted the report using the exec file and command

java -jar jacococli.jar report jacoco.exec --classfiles Calculator.class --html "report" --name jacocoReport --sourcefiles "Calulator.java"

However, the test coverage in the html report I made was 0%.

Here is my questions:

1. Do you know why my coverage is 0%?

2. Is there any problem in trying to extract the coverage result I want?

3. When calculating the coverage of the Calculator.java file by CalculatorTest.java code and extracting the report, is it correct to write --classfiles only using Calculator.class?

4. There is no difference in the results even if you insert both Calculator.java and CalculatorTest.java in --sourcefiles. Did I put it wrong? Or what is the effect of --sourcefiles?

And this is the Internet pages I referenced:

• https://github.com/junit-team/junit4/wiki/Getting-started
• Jacoco report in command line