Numbers in

About Numbers

One of the key aspects of working with numbers in Java is the distinction between integers (numbers with no digits after the decimal separator) and floating-point numbers (numbers with zero or more digits after the decimal separator).

Java has other datatypes apart from int and double:

// 8-Bit Integer
byte   a = 127;

// 16-Bit Integer
short  b = 262143;

// 64-Bit Integer
long   d = 18446744073709551999L;

// 32-bit Single-Precision Floating-Point
float  e = 5409.29f;

Both integers and floating-point numbers can use the _ character as a digit separator, which can help when defining large numbers:

int largeInt = 1_000_000;
// => 1000000

double largeDouble = 9_876_543.21;
// => 9876543.21

Arithmetic is done using the standard arithmetic operators (+, -, *, etc.). Numbers can be compared using the standard comparison operators (<, >=, etc.) along with the equality operator (==) and inequality operator (!=).

5 * 6
// => 30

1.2 > 0.8
// => true

120 == 100
// => false

2 != 4
// => true

When converting between numeric types, there are two types of numeric conversions:

1. Implicit conversions: no data will be lost and no additional syntax is required.
2. Explicit conversions: data could be lost and additional syntax in the form of a cast is required.

As an int has less precision than a double, converting from an int to a double is safe and is thus an implicit conversion. However, converting from a double to an int could mean losing data, so that requires an explicit conversion.

int i = 9;
double d = 2.72;

// Safe conversion, thus implicit conversion
double fromInt = i;

// Potentially unsafe conversion, thus explicit conversion
int fromDouble = (int)d;