Java Program to Toss a Coin

Tossing a coin is a random event and probability is 0.5 for both sides. So lets use Math.random for generating a random number between 0 and 1 and depend on this random value, we will produce a coin value (head or tail).

double rand=Math.random();
String coin="";
if(rand < 0.5)
	coin="Head";
else
	coin="Tail";
	        
System.out.println(coin);

This code will produce a single head/tail simulation result. Let's increase the number of attempts and calculate probability of each result.

Example: Tossing a coin 10 times

for (int i=1; i<=10; i++)
{
	double rand=Math.random();
	String coin="";
	if(rand < 0.5)
	   coin="Head";
	else
 	   coin="Tail";
	        
System.out.print(coin+" ");
//Tail Head Tail Tail Head Tail Head Head Head Tail 
}

Example: Tossing a coin 10 times and Calculating Probabilities

int head=0, tail=0;
for (int i=1; i<=10; i++)
{
    double rand=Math.random();
    String coin="";
    if(rand < 0.5)
    	head++;
    else
    	tail++;
}
System.out.println("Head Probability:"+(head)/10.0);
System.out.println("Tail Probability:"+(tail)/10.0);	

My Output for 10 attempts:

Head Probability:0.7
Tail Probability:0.3
 

Example: Tossing a coin 1000 times and Calculating Probabilities

Note: we expect probabilities to converge to 0.5 as the number of attempts increases. For ease of use, let's create a variable ofor number of attempts.

double head=0, tail=0;
int numberOfAttempts=1000;
for (int i=1; i<=numberOfAttempts; i++)
{
    double rand=Math.random();
    String coin="";
    if(rand < 0.5)
    	head++;
    else
    	tail++;
}
System.out.println("Head Results:"+head);
System.out.println("Tail Results:"+tail);	

System.out.println("Head Probability:"+(head)/numberOfAttempts);
System.out.println("Tail Probability:"+(tail)/numberOfAttempts);

My Output:

Head Results:497.0
Tail Results:503.0
Head Probability:0.497
Tail Probability:0.503