Scanner (java.util): interactive programs
nextInt()
nextLine()
nextDouble()
nextFloat()

Scanner scan = new Scanner(System.in);
scan.nextDouble();

String (java.lang): sequences of characters
Random (java.util): create random values (discrete, continuous)

---> Math: java.lang
1st observation: all the methods of Math are static
==> I can use the method through the class name

Math.pow(3, 2) ---> 9.0
Math.pow(4, 0.5) ---> 2.0
Math.pow(4, 1/2) ---> Math.pow(4, 0) ---> 1.0

Math.sqrt(9) ---> 3.0

Math.max(1, 2) ---> 2

int a = 1, b = 2, c = 3;
Math.max(c, Math.max(a, b)) ---> 3

int max = Math.max(a, b);
max = Math.max(c, max);

Math.ceil(4.5) ---> 5.0
Math.floor(4.5) ---> 4.0

Math.random() ---> [0.0; 1.0[

(int) (Math.random() * 6 + 1) ---> {1, 2, 3, ..., 6}

Math.PI ---> constant defined inside the Math class

Math.cos(Math.PI / 2)

Example#1: 
You will read the coefficients of a Quadratic equation from the user and then print the 
roots of the equations to the screen. 
ax^2 + bx + c

delta = b^2 - 4ac
root1 = -b + sqrt(delta) / (2a)
root2 = -b - sqrt(delta) / (2a)

a = 1, b = 2, c = 1

x^2 + 2x + 1 = (x + 1)^2

- DecimalFormat class (java.text)
The methods of DecimalFormat are not static


03456789

DecimalFormat fmt = new DecimalFormat("00000000");

DecimalFormat fmt = new DecimalFormat("0.##");
fmt.format(2.346) ---> "2.35"

2.35 + "" ---> "2.35"
"2.35" ----> 2.35

- Wrapper classes

byte ---> Byte
short ---> Short
int ---> Integer
long ---> Long

float ---> Float
double ---> Double

char ---> Character
boolean ---> Boolean

- Let us read two double values from the user: 
Enter val1: 23.5
Enter val2: 24.6

Calculate the average of the fractional parts of these values. 
















 























