Primitive data types in Java - ilya-khadykin/notes-outdated GitHub Wiki

Primitive data types in Java

Primitive type is basically a cell in computer memory which holds particular value

Primitive types are passed by value, not by reference, so that their value is copied.

  • boolean
  • char
  • byte, short, int, long
  • float, double

boolean

boolean can have only true or false as values. It's impossible to convert other primitive types to boolean like this boolean b = 10;

boolean is returned when comparison operator is used: < <= > >= == !=

It supports the following logic operators: ! && || ^ | & or &= |= ^=

public boolean booleanExpression(boolean a, boolean b, boolean c) {
  return (c & secretFunction()) || (a ^ b);  // & is used instead of && because secretFunction() should always be called
}

byte, short, int, long

Type Size (bit) Range
byte 8 -128 ... +127
short 16 -215 ... +215-1
int 32 -231 ... +231-1
long 64 -263 ... +263-1 
int decimal = 99;

int octal = 0755;

int hex = 0xFF;

int binary = 0b101;

int tenMillion = 10_000_000;

long tenBillion = 10_000_000_000L;  // long

Overflow isn't consider as an error:

byte b = 127; // 01111111
b++; // 10000000 == -128
int neg = ^a;

int and = a & b;

int or = a | b;

int xor = a ^ b;

int arithmeticShiftRight = a >> b;  // % 32

int logicalShiftRight = a >>> b;

int shiftLeft = a << b;

char

16 bit, unsigned; 0 .. 216-1

Returns Unicode code UTF-16

float, double

Type Size (bit) Sign Stagnat Exponent
float 32 1 23 8
double 64 1 52 11

+-m2e IEEE 754

double simple = -1.234;

double exponential = -123.4e-2; // -123.4 * 10^2

double hex = 0x1.Fp10; // 1.F * 2^10

float floatWithSuffix = 36.6f;

double doubleWithSuffix = 4d;
double positiveInfinity = 1.0 / 0.0; // Infinity, not an error

double negativeInfinity = -1.0 / 0.0; // Infinity, not an error
// 1/Infinity == 0

double nan = 0.0 / 0.0;

boolean notEqualIsItself = nan != nan;

comparison of float, double

|a-b| <= epsilon where epsilon is measure of inaccuracy

Reference types

All none primitive types. This type holds a reference to a cell in computer memory where the actual data is stored

null (String u = null;) shows that the variable doesn't have any reference and is empty.

  • Strings;
  • all classes.
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