Numerics&Operators

Question 1

Cela cisla - defaultni typ
kolik je min, pokud znam max

Answer 1

0 … int
0l … long

-(max)-1
napr. pro 127 je to -128

Question 2

byte - pamet, max

Answer 2

1 byte
127

Question 3

short - pamet, max

Answer 3

2 bytes
32 767

Question 4

int - pamet, max

Answer 4

4 bytes
2 147 000 000 2 miliardy

Question 5

long - pamet, max

Answer 5

8 bytes
9 223 000 000 000 000 000 (9.223 * 10^3*6) 9 trilionu

Question 6

Desetinna cisla - defaultni typ
Dva typy zapisu

Answer 6

0 … double
0f … float

123.456
1.23456E2

Question 7

float - pamet

Answer 7

4 bytes

Question 8

double - pamet

Answer 8

8 bytes

Question 9

signed integer - jak je ulozen

Answer 9

dvojkovy doplnek:
pro zaporne cislo odecti 1 a prevrat vsechny bity

Question 10

Automaticke castovani

Answer 10

Lze jen z mensiho typu na vetsi
Napr. int to long, float to long

Question 11

char - pamet, default, rozsah

Answer 11

2 bytes
\U0000
0 - 64 535

Question 12

char - druhy zapisu (4)

Answer 12

‘X’
unicode (hex) \uXXXX
ascii (octal) \XXX
escape sequences \r \n \t \f ' " \

Question 13

auto-boxing
auto-unboxing

Answer 13

auto-boxing: zabaleni int do Integer
auto-unboxing: rozbaleni Integer na int
caste pouziti ubira na vykonu!

Question 14

vlastnosti wrapper classes (2)
konstanty (2)

Answer 14

jsou signed
jsou immutable

MIN_VALUE, MAX_VALUE

Question 15

Metody wrapper classes:
tvorba z primitivu
tvorba ze stringu
rozbaleni do primitivu

Answer 15

Integer.valueOf(5);
Integer.parseInt(“5”);
integer.intValue();

Question 16

prevedeni primitivu na String

Answer 16

String.valueOf(5);

Question 17

Typ pouzivany tam, kde je vyzadovana desetinna presnost (finance)
Cim lze tu presnost zmatlat
Co pouzit misto toho

Answer 17

BigDecimal
new BigDecimal(x)
BigDecimal.valueOf(x)

Question 18

BigDecimal - jak se dela scitani, odecitani, nasobeni, deleni, modulo
Rozbaleni do double
Konstanta pro male cislo

Answer 18

bd.add(other); subtract / multiply / divide / remainder
- primitivni operatory nefunguji!!!
bd.doubleValue()
BigDecimal.ONE

Question 19

BigDecimal - nastaveni presnosti na dve des. mista s beznym zaokrouhlovanim

Answer 19

bd.setScale(2, RoundingMode.HALF_UP)

Question 20

Deleni - operator, kdy neni celociselne

Answer 20

/
pokud je delitel (to druhe) desetinny

Question 21

Co porovnava ==

Answer 21

hodnotu na stacku
tedy pro primitivy obsah
pro objekty reference

Question 22

Automatic casting u ciselnych primitivu: poradi

Answer 22

byte > short > int > long > float > double

Question 23

Typ vysledku u primitivnich cisel

Answer 23

pro typy mensi nez int je vysledek int (short + byte = int) - cisla v rovnici se prevedou pred operaci na int
pro ostatni je podle nejvetsiho typu (int + float = float)

Question 24

Co udela operace byte 127+5

Answer 24

Compilation error, type overflow

Question 25

Logicke operatory short-circuit long-circuit

Answer 25

Short-circuit: && || - prava strana se nemusi vyhodnotit Long-circuit: & | ^(xor) - vyhodnoti se vse

Question 26

jak spocitam kosinus, arckosinus, sinus, tangens

Answer 26

Math.cos(x), acos, sin, tan

Question 27

jak spocitam e^x, x^y, odmocnina x

Answer 27

Math.exp(x) Matc.pow(x, y) Math.sqrt(x)

Question 28

funkce pro minimum, maximum, zaokrouhleni cisla

Answer 28

Math.min() Math.max() Math.round()

Question 29

Jak ziskam nahodne cislo, jaky bude jeho rozsah

Answer 29

Math.random() - bude mezi 0 vcetne a 1

Question 30

Serad priority operatoru bit shift, scitani, nasobeni, relacni (>, <), post&prefix

Answer 30

post&prefix nasobeni scitani bit shift relacni operatory

Question 31

Serad prioridy operatoru relacni, ternarni, rovnost, prirazeni, bitove &|^, logicke &|

Answer 31

relacni rovnost bitove logicke ternarni prirazeni

Question 32

Logicke operace nad byte

Answer 32

I or, & and, ^ xor dam v binarnim kodu pod sebe a scitam

Question 33

Byte shift - 3 druhy, jak funguji

Answer 33

>> signed right shift - posune a doplni zleva nuly nebo jednicky podle znamenka; x >> 3 = x / 2^3 << signed left shift - posune a doplni zprava nuly; x << 3 = x * 2^3 >>> unsigned right shift - posune a doplni zleva nuly (-> pro zaporna cisla nefunguje dobre)

Question 34

Zkracena forma pro x = x>>>5

Answer 34

x >>>= 5

Question 35

Jakeho typu je vysledek, pokud b je typu byte? var result = +b;

Answer 35

int