Programming Laboratory

Summary of 1st classes

What do should know after the first class:

* The project is divided into source catalogs - src, test files - test, resources - resources. Each of them having its specific purpose.

* In the project directory there is a file called pom.xml containing Maven settings, in this file we add links to external libraries and settings for building the application.

* The logger settings can be found in the file log4.properties in the resources directory. Whenever we use other library that require settings we put them in an appropriate named file in the resources directory.

* We work with Git branches - every new functionality (class topic) is assumed to be on a separate branch.

Git refresh changes from repository

In order to download changes (synchronize) with Git repository, click Ctr + T, and if it does not help, choose VCS-> Git-> Fetch from the menu.

Synchronization of the Git code with the original repository

Go to VCS -> Git -> Remotes

Add entry for the host repository

https://github.com/WitMar/PRA2020-PRA2021

give it some name.

Choose Ctrl + T to refresh dependencies.

If it does not work in order to download the changes select VCS -> Git -> fetch.

Then, on the branch list in the bottom right corner of the screen, you should see the branches from Class and from your repository.

Go to branch TestAndDebugStart

Since we are moving into new repository it is possible that you need to set up maven again. Go to Maven Tab and check if you see the goals (Lifecycle, Plugin, Dependencies) if not try to refresh Maven. If this does not help choose the little plus and choose pom.xml from your local hard drive. Afterward click refresh in Maven again. That should help - check if your .java files have green circle next to them in the Project view tab.

Useful IDE shortcuts in IdeaJ

List of IdeaJ shortcuts:

https://resources.jetbrains.com/storage/products/intellij-idea/docs/IntelliJIDEA_ReferenceCard.pdf

Alt + Enter (or a ligthbulb) show a hint for the IDE error solution

Ctrl + W, Ctrl + Shift + W select the entire section, extend the selection, narrow the selection.

Ctrl + Shift + F search string in Project

Ctrl + Shift + N search for a file by name

Shift + Shift search everywhere

Alt + Insert generate code

Ctrl + / comment on the line

Ctrl + Shift + / uncomment lines

Ctrl + E files last opened

Ctrl + Alt + L format the code with default formatting settings

Tab, Shift + Tab indent, undo indent

Shift + F6 change the name

Ctrl + Shift + Alt + T refactor

Ctrl + Alt + M Extract the method

Alt + Right / Left go to next previous tab

Ctrl + Alt + Right / Left navigate back/forward

Alt + F7 find usages

Ctrl + (click on method name) show usage

Ctrl + Alt + (click on method name) show the implementation

Ctrl + K is used to commit the code locally to the repository

Ctrl + Shift + K is used to commit code to an external repository

Ctrl + T is used to refresh the project - download changes from the server

Attention!! If you use Linux or other non-Windows operating system (or a remote desktop) some of those shortcuts might be already reserved in the system, then you either need to change the system settins or change them in Settins->Keymap in Intellij

Task

Move (if you are not there yet) to branch TestAndDebugStart.

Search for a class named ClassThatHaveItAll (Ctrl + Shift + N).

Format the code (Ctrl + Alt + L) in computers at University for system linux this shortcut is design to log out from account. Change the shortcut setting in the system if you want to use this shortcut in IntelliJ.

Add to the class a parameter

List<Long> list;

Choose an automatic error correction (Alt + Enter).

Then select (Alt + Insert) to generate the constructor, and setters and getters for the class.

Find the interface called InterfaceOne (Ctr + Shift + f). Search for the use and implementations of the method printMe() (Ctrl + click on the method name) by clicking on either the definition or the usage of the method.

Find usages of the method printMe (Alt+F7).

Check how to move between tabs (Alt + right/left) and navigate to previous changes (Ctrl + Alt + right/left).

Debug

You can run code execution in Debug mode by choosing Run -> Debug or by choosing the right mouse button on the class and then Debug.

You can also click on the green triangle next to the class name to Run or Debug the Class

What is debugging?

https://www.codeproject.com/Articles/991643/What-is-Debugging-How-to-Debug-A-Beginners-Guide

Helpful in debugging are the so-called breakpoints, places in which we want the execution to stop in execution so that we can check variables values. To add a breakpoint, click next to the line number so that a red dot appears.

After clicking right mouse button on the dot, we can also specify a special condition on which the breakpoint should work.

After launching the debug mode, the debug window appears on the bottom of the screen. You can find there the current values of the variables. Additionally, we can choose by Alt + F8 or by clicking on the calculator icon a window for evaluation of expressions. Expression can be useful in debugging large structures like lists which are hard to go through one-by-one.

With the appropriate settings, it is also possible to debug applications running on the server at runtime (more on this subject in future classes).

Task

Run the Breakpoints class. What error has occurred ?

Debug the execution of the class Breakpoints.

To stop the call, add a breakpoint in the class.

Use F8 (or the down arrow on the debug panel) to move the code execution line by line.

Use StepInto - F7 (right-down arrow on the debug panel) to enter the method call.

Find and correct the error.

Task

Start the class EvaluateExpressions. What error has occurred?

Set the breakpoint in the ProcessElementAtIndex method.

Open the evaluation window and enter in it a line list.get(index).

Choose F9 (green triangle on the debug panel) to movo onto the next breakpoint execution and preview the variable values.

To check how the list look like enter in evaluation window

Collections.reverse(list);
list

Find and correct the error.

Task

Run the class ConditionalBreak. What error has occurred?

On line 18, set the normal breakpoint is it easy to find the error?

Set the conditional breakpoint to stop when !everythingIsOk.

As you might notice breakpoint is not working, move it to the line 19.

Run the code, what caused the error?

Shelve ans Stash

Shelve

Sometimes you need to switch between different tasks with things left unfinished and then return back to them. IntelliJ IDEA provides you with a few ways to conveniently work on several different features without losing your work:

• create new branch for separate code

• stash or shelve pending changes

Stashing changes is very similar to shelving. The only difference is in the way patches are generated and applied. Stashes are generated by Git, and can be applied from within IntelliJ IDEA, or outside it. Patches with shelved changes are generated by IntelliJ IDEA and are also applied through the IDE. Also, stashing involves all uncommitted changes, while when you put changes to a shelf, you can select some of the local changes instead of shelving them all.

You cannot shelve unversioned files, which are files that have not been added to version control.

In the Local Changes view on Git tab under the code, right-click the files or the changelist you want to put to a shelf and select Shelve changes from the context menu.

JUnit

JUnit is the most popular library for writing code tests in Java. The tests are aimed at controlling the quality of the code, check various call paths, as well as maintain error-free state of the code.

The Maven build process by default runs all tests in the process of creating an executable file.

First, we need to add in the pom.xml file the dependence for the test module.

https://mvnrepository.com/artifact/junit/junit/4.12

In our branch, a test class is already created, but to add a new one, the following operations should be performed:

Enter the class AdvanceMath and select Ctrl + Shift + T, click create to create new Test. To achieve the same thing differently you can choose the class name and click Alt + Enter and select create test.

The JUnit library uses the so-called annotations. Before each method that is designed to be run as a test, we put @Test.

Another important annotation is @Before which allows us to define the operations that will be performed before running each test.

Sample testing class:

package second.junit;

import org.apache.log4j.Logger;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

import static org.junit.Assert.*;

public class AdvanceMathTest {

    AdvanceMath math;
    final static Logger logger = Logger.getLogger(AdvanceMath.class);

    @Before
    public void setUp(){
        logger.info("Run setUp");
        math = new AdvanceMath();
    }

    @Test
    public void additionTest() {
        Integer a = math.addition(1,4);
        assertTrue(a==5);
    }

    @Test
    public void additionTestString() {
        long a = math.addition("1",4);
        Assert.assertEquals(5L, a);
    }


    @Test(expected = Exception.class)
    public void additionTestString2() {
        int a = math.addition("a1",4);
    }

}

You can run the test by clicking on the class and choosing run or by the Maven tab -> Test. Tests are also executed automatically when you perform Install in Maven.

Examples of using the JUnit library:

http://www.mkyong.com/tutorials/junit-tutorials/

It is recommend you to look at examples on how to test lists and maps.

Extra

function foo() {
    if ($maybe) {
        do_it_now();
        again();
    } else {
        abort_mission();
    }
    finalize();
}

function foo()
{
    if ($maybe)
    {
        do_it_now();
        again();
    }
    else
    {
        abort_mission();
    }
    finalize();
}

studentsCounter;
listIterator;
averageOverLastWeek;
findBestInClass();
computeAverage();

NightShift;
FastCar;

DAYS_IN_THE_WEEK();
NUMBER_OF_SHIFTS();

a += b , c = 0; (a == b)

if (value) {, public class A {

for (int i = 0; i < length; i++)

(int) value , (String) value