GameFrame | Game Frame Source -

You try to set Icon only when button is clicked. Instead of that, set it at the beginning when you create JButton. Otherwise, when you perform checking and you get the icon it will be null because this object isn't created with a button. You can set it after creating button e.g.:

As proposed by camickr use Shape for easy collision detection.
The following is a one-file mre (copy paste the entire code into ShapesCollision.java and run) of a basic implementation of it:

To compile via command-line, use javac rather than java. See the documentation for javac.

The java tool is for running classes that have already been compiled. For multiple classes, you should put them into a Java ARchive file (JAR) file. You include a manifest file that siecifies which class has a main method to be used for launching.

As you discovered, Java 11 gained a convenience feature where a single source-code file with a main method can be compiled and executed by simply calling java. The javac tool is implicitly called on your behalf. See JEP 330: Launch Single-File Source-Code Programs.

FYI, most of use an IDE to do this compiling and packaging for us rather than manually calling the command-line tools. I recommend you do the same.

You have a choice of at least three astoundingly good IDEs, each with a wide-range of features. Listed here in random order:

• NetBeans by the Apache Foundation
• Eclipse by the Eclipse Foundation
• IntelliJ by JetBrains

All three are available free-of-cost, with JetBrains also offering a paid Ultimate edition in addition to their free Community edition.

All three of these tools support using Apache Maven or Apache Gradle as the dependency-management and build-automation tooling. So you can choose to make your project portable across IDEs.

Here is quick tutorial using IntelliJ with Apache Maven.

Choose File > New > Project. In the "New Project" dialog, click Maven on the left. Check Create from archetype. Scroll down to org.apache.maven.archetypes:maven-archetype-quickstart. Expand that item to choose RELEASE. Click Next button.

Name you project something like MyFirstDemo. This is the name of the project folder created on disk. Expand the Artifact Coordinates. Change GroupId to something for you, like com.esau.demo. Convention is to use the reverse of a real domain you own, or invent something unlikely to cause a collision in naming. Change ArtifactId to the name of your .jar file that we will eventually produce. Perhaps just "MyFirstDemo", but it can differ from project name if you want.

Click Next to Maven screen. IntelliJ comes with a copy of Apache Maven bundled. No changes, click Next.

Wait a moment as your project is created. This may take a moment as often a Maven POM (configuration) file expands itself and then creates the project, and downloads needed libraries.

Edit your POM. I suggest changing:

You never called boom function. That's the issue.

Any number of ways you might do this, but one might be to take the common state information you need and apply it to a method, for example...

Start by getting rid of

I reworked your code and got your snake to draw and move. Here's the revised GUI.

The green block is the head of the snake. The yellow blocks are the body of the snake.

The snake is moving east at a rate of one block a second.

I created a Snake plain Java getter / setter class to hold a snake. I modified the move method in your GamePanel class to use the List that holds the snake.

I rearranged the JFrame method calls in your GameFrame class so they would execute in the correct order.

I commented out some code so I could test easier.

You'll need to code the rest of the snake game. I hope this helps you get going.

Here's the complete runnable code. I made all the classes inner classes so I could post this as one block of code.

Why is my game getting slower after several buildings,

Java Math uses angles in radians.
So calculate alpha in radians like this: