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*Variables can be given any value that matches their type. The Java statement that gives a variable its value *

**is called an **assignment **statement.**

*After a variable is given a value, the variable is *

**said to be **initialized**.**

*These aren’t equations! Read “=” as “gets” deposit = 4; my_num = 3.4; name = “CSC 130”;*

*You can use the assignment operator (=) and math operators (*,/,+,-) to do arithmetic.*

*Remember your order of operations! (PEMDAS) *

*The thing on the left gets changed.*

*value = 4+3*10;*

*interest = 3.0/2.0;*

*due = value+interest;*

The right-hand sides are

**expressions**

, just like in math.

*The following table summarizes the arithmetic operators available in Java.*

This is an integer division where the fractional part is truncated.

*We can change the value of a variable. If we want the value to remain the same, we use a *

**constant**

*.*

*final double PI = 3.14159; final int MONTH_IN_YEAR = 12; final short FARADAY_CONSTANT = 23060;*

The reserved word

**final**

is used to declare constants.

These are constants, also called named constant .

These are called literal constant.

*Block of code: Denoted by { }*

*Scope: The area of code in which a variable is available for use A variable’s scope is the block in which it is declared*

*1.*

*2.*

*3.*

*4.*

*5.*

*You must declare and initialize a variable before using it on the right of a rule.*

*Only the variable to the left of the = gets changed There can be one and only one variable on the left.*

*You cannot put data into a variable that does not match the variables’ type.*

*You can only have one variable with any given name in a particular block.*

*Assignment statements are NOT math equations!*

*count = count + 1;*

*These are commands!*

*value = 2;*

*interest = value;*

*value = value + 3;*

*What’s the value of interest?*

*There’s no such thing as:*

*z*

4(

*y*

3

*x*

12)

*Double Division: no rounding*

*3.0 / 6.0*

*6.0 / 3.0*

*x/1.5*

*At least one number must have a decimal*

*Integer Division: round DOWN*

*3/6*

*6/3*

*x/y, if both x and y are ints*

*Both numbers are integers*

*int x = 6/4;*

*int y = 4/6;*

*double z = 4/6;*

*double a = 6/4;*

*double b = 6/12.0;*

*int c = 6.0/12;*

*Modular Arithmetic: Remainder from division*

*Works with integers only*

*Operator is % (NOT PERCENT!) 6 % 4 is read “six mod four”*

*3 % 6 =*

*7 % 2 =*

*7 % 14 = *

*14 % 7 =*

*What useful thing does % 10 do?*

*3 % 10 = *

*51 % 10 =*

*40 % 10 =*

*678 % 10 = What useful thing does /10 do (integer division?)*

*3/10 =*

*51/10 = *

*40/10=*

*678/10 = What useful thing does % 2 do? *

*To change a variable’s type, you can cast from one type to another*

*int x = 4;*

*double y = 10/(double)x;*

*This is illegal:*

*int x = 5.5;*

*This is legal:*

*int x = (int)5.5;*

*Increment Operator*

*x =x + 1;*

*x++;*

*Decrement Operator*

*x = x – 1;*

*x--;*

*And others:*

*x += 2;*

*amount *= 1.05;*

*Random numbers – generate with the Math object.*

*Random double between x and y:*

**double rand = Math.random()*(y-x)+x;**

*Random int between x and y (inclusive):*

**int rand = (int)(Math.random()*(y-x+1)+x); Be careful with parentheses!**

*You can print to the console window:*

System.out.println(“Hello!”); String word = “Hey”; System.out.println(word); System.out.println(45+5); int y = 45+5; System.out.println(y); System.out.println(“y”); System.out.println(“The answer is “+y); System.out.print(“Stay on this line “); System.out.print(“and keep printing.”);

*Average three numbers*

*Fahrenheit to Celsius*

*C = (5/9)(F-32)*

*Given a big number, (> 1000), print its last three digits in reverse order (Ex: if input is 1234, prints out 432) *