Percentage chance of saying something?

Question

I want to write a program that:

• 80% of the time will say sendMessage("hi");
• 5% of the time will say sendMessage("bye");
• and 15% of the time will say sendMessage("Test");

Does it have to do something with Math.random()? like

if (Math.random() * 100 < 80) {   sendMessage("hi"); } else if (Math.random() * 100 < 5) {   sendMessage("bye"); } 

Answer 1

Yes, Math.random() is an excellent way to accomplish this. What you want to do is compute a single random number, and then make decisions based on that:

var d = Math.random(); if (d < 0.5)     // 50% chance of being here else if (d < 0.7)     // 20% chance of being here else     // 30% chance of being here 

That way you don't miss any possibilities.

Answer 2

For cases like this it is usually best to generate one random number and select the case based on that single number, like so:

int foo = Math.random() * 100; if (foo < 80) // 0-79     sendMessage("hi"); else if (foo < 85) // 80-84     sendMessage("bye"); else // 85-99     sendMessage("test");