Variables

Assignment

int x = 0; // Create a variable x, which is bound to 0

Variable definition follows the following syntax: <type> <name> = <binding>;

Multiple Declarations

Java supports multi-line definitions

Initializing and Binding Variables

double a, b, c; // Pure assignment
double x = 1.1, y = 1.2, z; // only x and y are bound

Primitive Types

In Java, 8 primitive types are supported, and String (total 9). Each of these is immutable

Tip

char is defined with a single quote

Tip

For precise calculations involving decimals, use BigDecimal instead of float or double, as floating points will result in rounding inaccuracies

Arithmetic

Integer - Integer division will result in a integer, but floored

Other mixed arithmetic operations will covert all the operands into doubles before dividing

Evaluation Rule

Java follows PEMDAS: Parenthesis, Exponents, Multiply, Divide, Add, and Subtract

Automatic Flooring

When defining an int, Java will automatically floor the calculation

Increments

int a = 0;
int b = a++;
System.out.println(a + " " + b); // 1 0
int c = ++a;
System.out.println(a + " " + b + " " + c); // 2 0 2

Tip

Java’s order of evaluation of a++ will bind b to a, then perform the ++ operation on a, incrementing the value of a. Likewise, ++a will increment, then bind.

The operation -- has the same behavior as ++, other than the fact that it subtracts

Arithmetic Assignments (same behavior as in Python)

+=, -=, *=, /=, %=

Doubles

`Double` Legalities

When assigning a integer value to a decimal, no error is produced, as Java will automatically covert it to a Double. The same goes for float

`Double` Base 10 Tips

When defining a variable that is equal to \(a\times10^b\), one may follow the form <a>E<b>

Booleans

A primitive type that only has two states: true and false

Negation

To negate, or invert, a boolean, use the ! operator