A list of IntelliJ tips and tricks.

Installing IntelliJ on Ubuntu

Use snap.

sudo snap install intellij-idea-ultimate --classic

Pycharm can be installed in the same way.

sudo snap install pycharm-community --classic

Install Java versions

In IntelliJ, go to:

  1. File
  2. New Projects Setup
  3. Structure
  4. Platform Settings > SDK
  5. Use the plus sign

Or install using the command line (for Ubuntu):

sudo apt install openjdk-17-jdk openjdk-17-jre

IntelliJ and markdown

I can’t remember if this plugin was installed by default. Markdown plugin.

Otherwise, install:

  1. In IntelliJ go to marketplace
  2. Ctrl + Alt + S to open Settings
  3. Go to Plugins
  4. Search Markdown and check it’s the same as the Markdown plugin above.
  5. Install

Customize Markdown

  1. Open Settings Ctrl + Alt + S
  2. Search for markdown and it should open in Editor/Color Scheme/Markdown

These are my settings:

  • Bold: Go to Style/Bold Text, on the right check Bold and Foreground. Change Foreground to F07178.
  • Italic: Go to Style/Italic Text, same color for Foreground.
  • Header: Go to Header/1st level header, set to Bold, also 2nd level header. Set Header marker same color as level headers.
  • Horizontal rule: Set Background to an orange color.

Soft Wrap Text

Use the shortcut Shift + Shift to open search. Type Soft wrap and select the result to have wrap text in the current opened file.

Alternatively open settings Ctrl + Alt + S, go to Editor/General, select Soft wrap these files and check that .md is included.

Template shortcuts

Type sout and TAB to autocomplete System.out.println()

Other shortcuts: main, foreach, ifn (if null statement), inst (is object instance of), iter (iterate iterable or array).

Use Ctrl + J to see other Java shortcuts. They are also under Settings then Editor then Live Templates.

Create a new project. HelloWorld example

  • File > New Project
  • Enter a name without spaces
  • Uncheck to add sample code
  • Right click on src > New Class
  • Follow the standard com.domain.package.Class such as com.example.helloworld.HelloWorld
  • Inside the created class, type main and autocomplete the rest.
  • Inside main brackets use Shift + Enter to create a new line
  • Type sout and tab to autocomplete.
  • Inside the println type "Hello world"
  • Run to build/compile (javac compiles to JVM bytecode to out directory) then JVM runs the bytecode.

Package the application in JAR

As seen on IntelliJ docs [here])(https://www.jetbrains.com/help/idea/creating-and-running-your-first-java-application.html#package). A JAR (Java archive) artifact is created like this:

Create an artifact configuration

  • File > Project Structure > Artifacts > + > JAR > From modules with dependencies
  • Main Class > open folder > select HelloWorld > OK > OK

Build the JAR artifact

  • Build > Build artifacts > HelloWorld.jar > Build

Run the JAR artifact

  • Ctrl+Shift+A > Edit configurations > Run/Debug configurations > + > JAR application
  • Name it: HelloWorldJar
  • In Path to JAR > click the folder > find the JAR file in out/artifacts/
  • In Before launch > + > Build Artifacts > select HelloWorld:jar

Execute run configuration

  • In the toolbar (top right), the dropdown changed from ‘Current File’ to ‘HelloWorldJar’
  • Click on Run

It should output similar to:

/usr/lib/jvm/java-1.17.0-openjdk-amd64/bin/java -Dfile.encoding=UTF-8 -jar 
/home/IdeaProjects/HelloWorld/out/artifacts/HelloWorld_jar/HelloWorld.jar

Hello World

Process finished with exit code 0

Add Java SDK API docs to project

  • File > Project Structure > Project > SDK > Edit > Documentation path
  • Click the + sign with the earth globe to add URL
  • Leave the default if applicable to the corresponding SDK version
  • OK
  • Browse over a word for example System in System.out.println
  • A popup shows the documentation for that word.

Move Code Around

Use Ctrl + Shift + arrow up/down

Generate toString()

As seen in IntelliJ docs here. The toString() method of the Java superclass java.lang.Object returns the string representation of the object.

  • By default it returns the name of the class and the object hash code
  • To override it and return the values of the object fields. Use the menu Code, then Generate, then toString().

Example Project:

src
  com.example.helloworld
    model
      Person
    HelloWorld

Example HelloWorld.java:

package com.example.helloworld;

import com.example.helloworld.model.Person;

public class HelloWorld {
    public static void main(String[] args) {
        Person person = new Person("Homer", "Simpson", 50);
        System.out.println(person);
    }
}

It outputs:

Example Person.java with override toString():

...
public Person(String firstName, String lastName, int age) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
}

@Override
public String toString() {
    return "Person{" +
            "firstName='" + firstName + '\'' +
            ", lastName='" + lastName + '\'' +
            ", age=" + age +
            '}';
}

Running HelloWorld.java again outputs person with the override:

Person{firstName='Homer', lastName='Simpson', age=50}

Extract Method

From the public class HelloWorld select the lines inside main.

  • Menu > Refactor > Refactor This > Extract Method
  • Rename the method and press Enter

It changed from:

public static void main(String[] args) {
    Person myPerson = new Person("Homer", "Simpson", 50);
    System.out.println(myPerson);
}

To:

public static void main(String[] args) {
    System.out.println("Hello World");

    myPerson();
}

private static void myPerson() {
    Person myPerson = new Person("Homer", "Simpson", 50);
    System.out.println(myPerson);
}

Debugging with break points

Expanding on my post on Debug with IntelliJ.

Using this example:

private static void myPerson() {
    Person myPerson = new Person("Homer", "Simpson", 50);
    System.out.println(myPerson);

    for (int i = 0; i < 100; i++) {
        System.out.println("The number i is: " + i);
    }
}

In IntelliJ, click on the left margin from the statement Person myPerson, to show a red dot.

Click on the bug icon to Debug.

Step over On the Debugger window, click on step over to move to the line System.out.println(myPerson). Click on step over again to move to the for loop.

Stop the debugger and debug again.

Step into Click on step into. It moves from Person myPerson to the Person.java class in the constructor definition. Use step over to move through the statements in the constructor. Then it moves back to statement creating the object Person myPerson.

Click on step over moves again to the next statement System.out.println(myPerson).

Step over (for loop) If you debug the for loop, there is no difference between step over and step into as it runs over each loop and it displays the result of each iteration on the right side of the statement.

for (int i = 0; i < 100; i++) {  i: 2
    people.add(new Person("Homer " + i, "Simpson", 50)); i: 2
    }

You can also add a condition to the break point.

  • Right click break point
  • In the Contition field enter i == 9
  • Then Resume Program
  • The for loop will go through 9 loops
  • Double click on people will show a popup ArrayList size = 9 with a + sign that will show the list of all 9 created objects.