Basics ====== **Printing to Console** println(str); // Example: println("Hello world."); **Variables** // Declare a variable var myVarName; // Initialize a variable var myVarName = 5; // Assign to an existing variable myVarName = 10; // Print a variable println(myVarName); println("The value is: " + myValue); **User Input** // Read a string var str = readLine(prompt); // Read an integer var num = readInt(prompt); // Read a float var cost = readFloat(prompt); // Example: var name = readLine("What is your name?"); var age = readInt("What is your age?"); **Comparison Operators** // Comparison operators return booleans (true/false values) x == y // is x equal to y x > y // is x greater than y x >= y // is x greater than or equal to y x < y // is x less than y x <= y // is x less than or equal to y // Comparison operators in if statements if(x == y){ println("x and y are equal"); } if(x > 5){ println("x is greater than 5."); } **Math** // Operators: + Addition - Subtraction * Multiplication / Division % Modulus (Remainder) () Parentheses (For order of operations) // Examples var z = x + y; var w = x * y; //Increment (add one) x++ //Decrement (subtract one) x-- //Shortcuts x = x + y; x += y; x = x - y; x -= y; x = x * y; x *= y; x = x / y; x /= y; **Random Numbers** // Random integer between low and high Randomizer.nextInt(low, high); Randomizer.nextBoolean(); Randomizer.nextFloat(low, high); Randomizer.nextColor(); var roll = Randomizer.nextInt(1,6); var color = Randomizer.nextColor(); Graphics ======== **Canvas** // returns the width of the canvas getWidth(); // returns the height of the canvas getHeight(); // Examples var height = getHeight(); // Returns the x coordinate of the center // of the canvas var center = getWidth() / 2; **All Graphics Objects** // To get the type of the object var type = obj.getType(); /*could return: 'Circle' 'Rectangle' 'Text' 'Line' */ **Circles** // To make a circle var circle = new Circle(radius); // Example, circle with 50px radius var circle = new Circle(50); circle.setPosition(x, y); circle.setColor(Color.red); circle.setRadius(100); // Change the radius // Add to screen add(circle); // move the circle dx horizontally and dy vertically circle.move(dx, dy); **Rectangles** // To make a rectangle var rect = new Rectangle(width, height); // Example, 200x50 rectangle var rect = new Rectangle(200, 50); rect.setPosition(x, y); rect.setColor(Color.blue); // Add to screen add(rect); // move the rect dx horizontally and dy vertically rect.move(dx, dy); **Lines** // To draw a line from (x1, y1) to (x2, y2) var line = new Line(x1, y1, x2, y2); line.setColor(Color.green); // Add to screen add(line); // move the line dx horizontally and dy vertically line.move(dx, dy); // change the starting point of the line to (x1, y1) line.setPosition(x1, y1); // change the end point of the line to (x2, y2) line.setEndpoint(x2, y2); **Text** // To make a graphical text object var txt = new Text(label, font); // Example var txt = new Text("Hello, world!", "30pt Arial"); txt.setPosition(x, y); txt.setColor(Color.blue); // Change what the text says txt.setText("Goodbye!"); // Add to screen add(txt); // move the text dx horizontally and dy vertically txt.move(dx, dy); **Color** // There are many color constants. You can set an objects // color like obj.setColor(color); // Specifically, obj.setColor(Color.RED); // List of available colors: Color.RED Color.GREEN Color.BLUE Color.YELLOW Color.CYAN Color.ORANGE Color.WHITE Color.BLACK Color.GRAY Color.PURPLE // You can also make your own color by giving a red, green, // and blue component like var color = new Color(r, g, b); // The values are between 0-255 for each component. // specifically var color = new Color(255, 24, 180); // Other fun functions // Return a random color var color = Color.randomRed(); var color = Color.randomGreen(); var color = Color.randomBlue(); // Get a random color from the randomizer var color = Randomizer.nextColor(); Control Structures ================== **Booleans** // A boolean is either true or false var myBoolean = true; var anotherBoolean = false; var result = readBoolean("Question? "); // Not Operator var x = !y; // x gets the opposite of y // And Operator var andExp = x && y; // Or Operator var orExp = x || y; // You can combine many booleans! var boolExp = x && (y || z ) If Statements, If/Else, If/Else If/Else if(BOOLEAN_EXPRESSION){ // code to execute if true } if(BOOLEAN_EXPRESSION){ // code if true }else{ // code if false } if(x < 0){ println("x is negative."); } if(color == "red" || color == "blue" || color == "yellow"){ println("Primary color."); }else{ println("Not a primary color."); } // You can use else if if you have multiple // conditions, but only one should happen. if(cond1){ }else if(cond2){ }else if(cond3){ }else{ } // You can always write these using nested // if/else, like if(cond1){ }else{ if(cond2){ }else{ //... } } **For Loops** for(var i = 0; i < COUNT; i++){ /* Repeat code betweeen * brackets COUNT times */ } /* Print numbers 0-9 */ for(var i = 0; i < 10; i++){ println(i); } **While Loops** while(boolean expression){ // Repeat code betweeen brackets while // 'boolean expression' is true } while(i > 10){ println(i); i--; } // This is a loop and a half format while(true){ // code if(condition){ break; } } Animation ========= **Timers** setTimer(fn, delay); // Create a timer stopTimer(fn); // Stop a timer // Example: call moveBall every 40 milliseconds function moveBall() { ball.move(x, y); } function start() { setTimer(moveBall, 40); } **Mouse Events** function start() { // Set up mouse callbacks mouseMoveMethod(onMouseMove); mouseClickMethod(addBall); mouseDragMethod(updateLine); } function onMouseMove(e) { println("Mouse is at (" + e.getX() + ", " + e.getY() + ")."); } function addBall(e) { var ball = new Circle(20); ball.setPosition(e.getX(), e.getY()); add(ball); } function updateLine(e) { line.setEndpoint(e.getX(), e.getY()); } **Keyboard Events** function start() { // Set up keyboard callbacks keyDownMethod(keyDown); keyUpMethod(keyUp); } function keyDown(e) { if (e.keyCode == Keyboard.LEFT) { ball.move(-5, 0); } if(e.keyCode == Keyboard.letter('K')){ println("You pressed K"); } } function keyUp(e) { println("You lifted up a key"); } **Misc** function start() { mouseClickMethod(turnRed); } // If you click on an object, turn it red. function turnRed(e) { var elem = getElementAt(e.getX(), e.getY()); if (elem != null) { elem.setColor(Color.red); } } Data Structures =============== **Arrays** // Create an empty array var arr = []; // Create an array with values var arr = [1, 2, 4]; // An array can have any type var arr = [4, "hello", x]; // Access an element in an array var elem = arr[i]; var firstElem = arr[0]; // Set an element in an array arr[4] = 9; // Looping over an array for(var i = 0; i < arr.length; i++){ var cur = arr[i]; // process cur } // length of an array var length = arr.length; // Add to an array arr.push(elem); // Pop last element from array var last = arr.pop(); // Finding an element in a list var index = arr.indexOf(5); // Remove an element from a list at index i arr.remove(i) **Maps/Objects** // Object literal var obj = { name: "Jeremy", color: "blue" }; // Objects/Maps have a collection of key, value pairs // Set a value obj["Jeremy"] = "123-4567"; // Get a value for a key var phone = obj["Jeremy"]; // Loop over an object for(var key in obj){ var val = obj[key]; // process key and val } **Sets** // Make a new set var set = new Set(); // Add to a set set.add(5); // Does a set contain a value set.contains(5); // returns a boolean // Number of elements in the set set.size(); // returns an integer **Grids** // Create a grid var grid = new Grid(rows, cols); // Get a value in a grid var elem = grid.get(row, col); // Set a value in a grid grid.set(row, col, val); // Getting dimensions var rows = grid.numRows(); var cols = grid.numCols(); // Is a row, col pair inbounds grid.inBounds(row, col); // Set all values in grid to initial value grid.init(0); // sets all grid values to 0 // Initialze a grid from an array grid.initFromArray([ [6, 3, 2], // 0th row [2, 5, 1], // 1st row [4, 3, 9], // 2nd row [1, 5, 1] // 3rd row ]);
