Part 2: Operators

Mar 25, 2020
Part 2: Operators
• Crash Course to Java

Part 2: Operators

Operators are used to use and manipulate variables.

Section A: Arithmetic
Arithmetic operators are used in mathematical expressions in the same way you would use them in Algebra. Say you have two integers: A has a value of 10, B has a value of 20.

+ (Addition): A + B would give you 30.

- (Subtraction): B - A would give you 10.

* (Multiplication): A * B would give you 200.

/ (Division): B / A would give you 2.

% (Modulus): Modulus divides and returns the remainder. B % A would give you 0.

++ (Increment): Increase the value by 1. B++ would make B 21.

-- (Decrement): Decrease the value by 1. B-- would make B 19.

Section B: Relational
Relational operators are all concepts you'll probably easily pick up, and you've probably seen some of them in algebra as well. They act as a boolean which can then be used in if statements, etc.

== (Equal to): Checks if two values are equal. A == B is false.

!= (Not equal to): Checks if two values are unequal. A != B is true.

> (Greater than): Checks if the left value is greater than the right value. A > B is false.

< (Less than): Checks if the left value is less than the right value. A < B is true.

>= | <= (Greater/Less than or equal to): Like >/< but will also be true if the values are equal. A >= B is false. A <= B is true.

Section C: Logical
Logical operators are used to return a boolean based on the boolean result of multiple expressions.

&& (And): Returns true only if both/all expressions are true. A <= B && A >= B is false. A <= B && A == 10 is true.

|| (Or): Returns true if any of the expressions are true, else returns false. A <= B || A > 50 is true. A > B || B == 20 is true. A > B || B == 5 is false.

! (Not): Reverses the expression it is applied to. !(A > B) is true. !(A < B) is false.

Section D: Assignment
Assignment operators are used to assign value to variables.

=: The most basic assignment operator. Just sets a value. C = A + B would set C to 30.

+=: Adds the right value to the left value and then sets the left value to the result. B += A would set B to 30.

-=: Subtracts the right value from the left value and then sets the left value to the result. B -= A would set B to 10.

*=: Multiplies the left value by the right value and sets the left value to the result. B *= A would set B to 200.

/=: Divides the left value by the right value and sets the left value to the result. B /= A would set B to 2.

Section E: Misc
There are a few other operators outside of those categories.

(? : ) Conditional Operator: A conditional operator, also known as the ternary operator, is used to evaluate a boolean value and decide what value should be there based on the boolean.
For example:
Code (Java):
private String getName() {
return this.name == null ? "default value" : this.name;
}
instanceof Operator: The instanceof operator is used to check if an object is of a particular type.
Code (Java):
private boolean isString(Object object) {
return object instanceof String;
}
isString("potato") would return true. isString(new Integer(5)) would return false.

Continue the guide in Part 3!