Gain insights into Java, a versatile and portable programming language. Delve into similarities with C++ and Python and learn essential Java-specific features with practical coding examples.

Looking to jump into a new programming language? Java is an easy-to-use, highly portable and ubiquitous language that is used for a variety of development purposes such as Android applications,  desktop applications, and website backend systems. Designed for programmers who are already familiar with coding in languages such as C++, Python, or other similar languages, this course articulates any Java-specific details that programmers need to know to get acquainted with the language and also highlights similarities and differences between Java and other languages through multiple coding examples.

The Complete Java Crash Course

Each falling piece in Tetrominos is made up of four small blocks arranged in a particular way. Let's write and test the `Block` class. Create a new file in your project called `Block.java`. To get you started, here's a skeleton of the code, which you may copy in:




import java.awt.Color;
import java.awt.Graphics;

class Block {

	public int colorIndex;

	public static Color[] colors = {Color.red, Color.blue, Color.magenta,
			Color.orange, Color.green, Color.cyan, Color.yellow};

	public Block(int colorIndex) {
	}

	public void draw(Graphics g, int scale, int x, int y) {
	}

}


Block.java


import java.awt.Color;
import java.awt.Graphics;

class Block {

	public int colorIndex;

	public static Color[] colors = {Color.red, Color.blue, Color.magenta,
			Color.orange, Color.green, Color.cyan, Color.yellow};

	public Block(int colorIndex) {
		this.colorIndex = colorIndex;
	}

	public void draw(Graphics g, int scale, int x, int y) {
		int px = x * scale + 1;
		int py = y * scale + 1;

		int size = scale - 2;

		g.setColor(colors[colorIndex]);
		g.fillRect(px, py, size, size);
	}

}


BlockSolution.java

# Task: write the constructor

Blocks come in several colors. To simplify referring to the colors, we use an array of colors, defined in the array `colors`. This array is `static` because, although we will create many blocks, there will be only one array of colors, accessible through the `Block` class.

Each block has exactly one instance variable, as we can see from the line `public int colorIndex`. If the block has a colorIndex of 2, then this would indicate that the block should be drawn using the magenta color. When a block is created using its constructor, the index of the color of the block should be passed in, and stored in the instance variable.

Write the body of the constructor, which should be only one line long. When you are done, you may check your work by looking at the second tab of the code above, `BlockSolution.java`.

# Task: write the `draw` method

The Block class maintains information about the color of the block, but nothing else. Still, the Block class is a useful place to put a method that draws a block of the proper color. Write the `draw()` method, which takes as parameters an x, y coordinate in **block coordinates**, and a scaling parameter `scale`. To find the pixel coordinates, multiply `x` and `y` by `scale`, and then use the Graphics object `g` to draw the rectangle. 


Add a new class to represent and draw individual square blocks in the Tetrominos game.

Hello, Java!

Variables and expressions

Flow of control: loops and conditionals

Classes, objects, and methods

Challenge project: tetrominos

Step 3: The Block class