Big task: Creating a game in Java

"Hi, Amigo!"

"Hi!"

"How are you to address a senior officer?"

"Sorry, sir."

"Hello, Captain Squirrels, sir."

"That's better."

"You have a new secret mission today."

"You need to write a space battle simulation."

"Cool! Uhh... I mean, I am ready, sir."

"It just so happens that I have an idea for it. How about this?"

"No, that's too difficult."

"We'll start with something simpler:"

"Hmm..."

"What? Still to difficult? Then let's make it even simpler."

"Contact Agent IntelliJ IDEA to receive the task. He already has it."

"Permission to ask a question, sir?"

"Speak."

"Why do you call IntelliJ IDEA an agent, sir? It's just a program."

"You're just a program."

"IDEA is an artificial intelligence and a crew member on our ship. Is that all clear? Get going already."

"Yes, sir! Carrying out your order, sir."

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Java Collections, level 3, lesson 15

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Space (part 1)

Let's write a new computer game. We'll have a spaceship that will shoot rockets at UFOs. For their part, the UFOs will lob bombs at the spaceship. And, of course, all this is happening in outer space. We're going to need the following classes: Space, Spaceship, and Ufo.

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Java Collections, level 3, lesson 15

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Space (part 2)

We will have bombs and rockets. That means we need Bomb and Rocket classes. Create them. Our classes will have a lot in common. They will move about in space and be drawn on the screen. That means that they'll all have coordinates and a size.

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Java Collections, level 3, lesson 15

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Space (part 3)

Why do we need the Space class? To store all the objects and control how they interact. What fields should it have? width and height. What else?

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Java Collections, level 3, lesson 15

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Space (part 4)

What is Space class missing? That's right! run() and draw() methods. If you recall, the run method manages all the game logic. And the draw method is responsible for drawing the next "frame". We'll also benefit from a sleep(int ms) method.

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Java Collections, level 3, lesson 15

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Space (part 5)

Now let's move on to the BaseObject class. I want to make some suggestions. First, for simplicity, treat all of our objects in space as circles. We'll draw them as shapes, just as before. But when calculating object collisions, we'll assume they are round. Doing it this way is much simpler.

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Java Collections, level 3, lesson 15

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Space (part 6)

But there's more. The BaseObject class needs more methods. For now, these will be empty draw() and move() methods. Subclasses will have to override them and implement the necessary functionality. Also add a die() method, which causes the object to die (isAlive = false).

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Space (part 7)

Now let's tackle the Canvas class. It will contain a matrix that we will "draw" on. The matrix has a width and height. And we'll use it to store characters (chars) rather than numbers (ints).

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Java Collections, level 3, lesson 15

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Space (part 8)

What are we going to do with Canvas? We'll draw on it (on its matrix). Therefore, we need two methods: public void setPoint(double x, double y, char c), public void drawMatrix(double x, double y, int[][] matrix, char c).

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Space (part 9)

Canvas needs another two methods. Write them. a) the clear() method(); This method will clear the matrix so it can be drawn on again. For example, replace all characters in the matrix with spaces. b) the print() method(); This method draws the matrix on the screen.

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Space (part 10)

Now we'll write the Bomb class. Everything is simple here. Bomb inherits BaseObject. Here's what we need: a) change the constructor.

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Space (part 11)

Now we'll write the Rocket class. It's almost the same as the Bomb class. But: a) Rockets fly upward (i.e. y is decreased by 1); b) We'll draw 'R' instead of 'B'.

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Java Collections, level 3, lesson 15

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Space (part 12)

Now let's do the ship. For complexity, we'll do this: if the user presses the left button, the ship will start moving to the left and continue to do so. If the user presses the right button, it will start moving to the right and continue to do so until it hits the edge.

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Space (part 13)

We now turn to the draw and move methods. In the move() method, you need to: a) increase x by dx; b) check to see whether the ship has moved beyond the boundaries of outer space [0, Space.game.getWidth()]. Use the checkBorders method. Bear in mind that the ship's width is equal to twice its radius.

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Space (part 14)

Now write the Ufo class. It's a bit more complicated than the Bomb class and simpler than Spaceship. You will need draw(), move(), and fire() methods. Also, don't forget about the constructor. The parameters are doubles, and UFO's radius will be equal to 3.

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Space (part 15)

We still have to finish the Space class. Implement the getAllItems method: The method should return one common list of all BaseObject objects. Implement the moveAllItems method: The method should move all the objects all at the same time.

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Space (part 16)

And a little bit more: Implement the createUfo() method: If the list of UFOs is empty, create a ship in the center at the top of the screen. Implement the checkBombs() method: You need to check whether a bomb collided with the ship.

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Space (part 17)

We need to finish the draw() method. We'll do something similar with the move method. I'll write it myself today.

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Space (part 18)

Make width and height bigger and you can play! Enjoy the game :)

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