The redraw() function makes draw() execute once. In this example, draw() is executed once every time the mouse is clicked.
Original Processing.org Example: Redraw
// All Examples Written by Casey Reas and Ben Fry // unless otherwise stated. // The statements in the setup() function // execute once when the program begins void setup() { size(200, 200); // Size should be the first statement stroke(255); // Set line drawing color to white noLoop(); } float y = 100; // The statements in draw() are executed until the // program is stopped. Each statement is executed in // sequence and after the last line is read, the first // line is executed again. void draw() { background(0); // Set the background to black y = y - 1; if (y < 0) { y = height; } line(0, y, width, y); } void mousePressed() { redraw(); }