| Data-type | Storage-size | Limits |
|---|---|---|
| Byte | 8 bits | -127 <= x <= 127 |
| Short | 16 bits | -32768 <= x <= 32767 |
| Int | 32 bits | -2147483648 <= x <= 2147483647 |
| Long | 64 bits | -9223372036854775808 <= x <= 9223372036854775808 |
| float | 32 bits | 7 digits precision |
| double | 64 bits | 15 digits precision |
| char | 16 bits | 65536 Unicode characters |
| boolean | 1 bit | false (default) or true |
Strings belong to the class string, it is not a data-type
Declare like:
int i = 33;
float f = 4,4545f;
double d = 643,435345123d;
char c = “A”;
boolean OK = true;
Variable-names must start with a letter and can contain digits, _ and $ characters but no spaces.
Conversion to another data-type is not always automatic
int number1 = 7;
int number2 = 2;
float result = number1 / number2; //result is an integer (3)
float result = number1 / (float) number2; // number2 is forced to float, the result will be float too.
boolean conversions:
b is the result of the comparison between i and 0
| int i = 1; boolean b = i ! = 0; // b will be true |
int i = 0; boolean b = i ! = 0; // b will be false |
int is 1 if b is true, 0 if b is false
| boolean b = true; int i = (b ? 1 : 0); // int will be 1 |
boolean b = false; int i = (b ? 1 : 0); // int will be 0 |
Operators are like in other languages:
| Operator | Action |
|---|---|
| * | Multiply |
| / | Divide |
| % | Modus (remainder of division) |
| + | add |
| – | subtract |
| ( ) | Force calculation order |
| >= | Bigger than or equal |
| <= | Smaller than or equal |
| == | Equal to |
| != | Not equal to |
| expr1 && expr2 | True if both expressions are true, expr2 is only calculated if needed (expr1 is true) |
| expr1 & expr2 | True if both expressions are true (AND) |
| expr1 || expr2 | True if expr1 or expr2 is true, expr2 is only calculated if needed (expr1 is false) |
| expr1 | expr2 | True if expr1 or expr2 is true (OR) |
| expr1 ^ expr2 | True if only one of the expressions is true (eXclusive OR) |
| ! expr | True if the expression is false |
| ~ expr | Invert bits (0101 => 1010) |
| expr1 >> int | Bitwise shift right expr1 int positions left bit is filled with sign |
| expr1 >>> int | Bitwise shift right expr1 int positions left bit is filled with 0 |
| expr1 << int | Bitwise shift left expr1 int positions left |
| = | Assign |
| *= | Multiply and assign int a = 2; int a *=3; // a will be 6 |
| +=, -=, /= %=, <<=, >>=, >>>=, &=, |=, ^= | Like *= for resp. add, subtract, divide, modulus and the other operators. |
| ++ | Add one int b = a++; \ Assign to b then add 1 int b = ++a; \ Add 1, then assign to b. |
| — | Subtract one (like ++) |