Java's Primitive Data Types
boolean: 1-bit. May take on the values true and false only.
byte: 1 signed byte (two's complement). Covers values from -128 to 127.
short: 2 bytes, signed (two's complement), -32,768 to 32,767
int: 4 bytes, signed (two's complement). -2,147,483,648 to 2,147,483,647.
long: 8 bytes signed (two's complement). Ranges from -9,223,372,036,854,775,808 to +9,223,372,036,854,775,807.
float: 4 bytes, IEEE 754. Covers a range from 1.40129846432481707e-45 to 3.40282346638528860e+38 (positive or negative).
double: 8 bytes IEEE 754. Covers a range from 4.94065645841246544e-324d to 1.79769313486231570e+308d (positive or negative).
char: 2 bytes, unsigned, Unicode, 0 to 65,535
Java's Primitive Data Types
boolean: 1-bit. May take on the values true and false only.
byte: 1 signed byte (two's complement). Covers values from -128 to 127.
short: 2 bytes, signed (two's complement), -32,768 to 32,767
int: 4 bytes, signed (two's complement). -2,147,483,648 to 2,147,483,647.
long: 8 bytes signed (two's complement). Ranges from -9,223,372,036,854,775,808 to +9,223,372,036,854,775,807.
float: 4 bytes, IEEE 754. Covers a range from 1.40129846432481707e-45 to 3.40282346638528860e+38 (positive or negative).
double: 8 bytes IEEE 754. Covers a range from 4.94065645841246544e-324d to 1.79769313486231570e+308d (positive or negative).
char: 2 bytes, unsigned, Unicode, 0 to 65,535
Java's Double class has members containing the Min and Max value for the type.
2^-1074 <= x <= (2-2^-52)·2^1023 // where x is the double.
Check out the Min_VALUE and MAX_VALUE static final members of Double.
(some)People will suggest against using floating point types for things where accuracy and precision are critical because rounding errors can throw off calculations by measurable (small) amounts.
Videos
Java uses the IEEE-754 binary64 format. In this format, one bit represents a sign (+ or − according to whether the bit is 0 or 1), eight bits are used for an exponent, and 52 bits are used for the primary encoding of the significant. One bit of the 53-bit significand is encoded via the exponent.
The values of the exponent field range from 0 to 2047. 2047 is reserved for use with infinities and NaNs. 0 is used for subnormal numbers. The values 1 to 2046 are used for normal numbers. In this range, an exponent field value of E represents an exponent e = E−1023. So the lowest value of e is 1−1023 = −1022, and the highest value is 2046−1023 = 1023. An exponent field value of 0 also represents the lowest value of E, −1022.
The 53-bit significand represents a binary numeral d.ddd…ddd2, where the first d is 0 if the exponent field is 0 and 1 if the exponent field is 1 to 2046. There are 52 bits after the “.”, and they are given by the primary significand field.
Let S be the sign bit field, E be the value of the exponent field, and F be the value of the primary significand field as an integer. Then the value represented is:
- if E is 1 to 2046, (−1)S • 2E−1023 • (1 + F•2−52),
- if E is 0, (−1)S • 2−1022 • (0 + F•2−52).
Now we can see the smallest positive number is represented when S is 1, E is 0, and F is 1 (00000000000000000000000000000000000000000000000000012). Then the value represented is (−1)0 • 2−1022 • (0 + 1•2−52) = +1 • 2−1022 • 2−52 = 2−1074.
The greatest finite number is represented when S is 1, E is 2046, and F is 252−1 (11111111111111111111111111111111111111111111111111112). Then the value represented is (−1)0 • 22046−1023 • (1 + (252−1)•2−52 = +1 • 21023 • (1 + 1 − 2−52) = 21023 • (21 − 2−52) = 21024 − 2971.
It's the same thing for floating-point values as for integer values - the number of bits available.
An IEEE double-length floating point value has 64 bits, used as follows:
Sign bit: 1 bit
Exponent: 11 bits
Significand precision: 52 bits
The significand is a binary fraction, the maximum value (all bits set) is therefore somewhat less than one.
The exponent has value 0 to 2047, or -1024 to +1023. That gives you the approximate range of 2 to the -1024 to 2 to the +1023 (it's actually less since a couple of values are reserved for specific use).
Wikiipedia for more exact details
I am learning Java, and am confuse on when to choose double or float for my real numbers or int. It feels like, it doesn’t matter because from my limited experience (with Java) both of them deliver the same results, but I don’t want to go further down the learning curve with Java and have a bad habit of using either messing up my code, and not having a clue as to why. So, when should you use float and double?
I’ve tried looking for definitive answers but the only difference I see seems to be based on the precision of the numbers?
Which data type is larger and which one is smaller?