What exactly does Double mean in java

Question

I m extremely new to Java and just wanted to confirm what Double is  Is it similar to Float or Int  Any help would be appreciated  I also sometimes see the uppercase Double and other times the lower case double  If someone could clarify what this means that d be great

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A double is an IEEE754 double-precision floating point number, similar to a float but with a larger range and precision.

IEEE754 single precision numbers have 32 bits (1 sign, 8 exponent and 23 mantissa bits) while double precision numbers have 64 bits (1 sign, 11 exponent and 52 mantissa bits).

A Double in Java is the class version of the double basic type - you can use doubles but, if you want to do something with them that requires them to be an object (such as put them in a collection), you'll need to box them up in a Double object.

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Double is a wrapper class      The Double class wraps a value of the   primitive type double in an object  An   object of type Double contains a   single field whose type is double       In addition  this class provides   several methods for converting a   double to a String and a String to a   double  as well as other constants and   methods useful when dealing with a   double    The double data type        The double data type is a   double-precision 64-bit IEEE 754   floating point  Its range of values is    4 94065645841246544e-324d to 1 79769313486231570e 308d  positive or negative     For decimal values  this data type is   generally the default choice  As   mentioned above  this data type should   never be used for precise values  such   as currency    Check each datatype with their ranges   Java s Primitive Data Types       Important Note   If you r thinking to use double for precise values  you need to re-think before using it  Java Traps  double

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In a comment on  paxdiablo s answer  you asked       So basically  is it better to use Double than Float     That is a complicated question   I will deal with it in two parts    Deciding between double versus float  On the one hand  a double occupies 8 bytes versus 4 bytes for a float   If you have many of them  this may be significant  though it may also have no impact    Consider the case where the values are in fields or local variables on a 64bit machine  and the JVM aligns them on 64 bit boundaries    Additionally  floating point arithmetic with double values is typically slower than with float values     though once again this is hardware dependent   On the other hand  a double can represent larger  and smaller  numbers than a float and can represent them with more than twice the precision   For the details  refer to Wikipedia   The tricky question is knowing whether you actually need the extra range and precision of a double   In some cases it is obvious that you need it   In others it is not so obvious   For instance if you are doing calculations such as inverting a matrix or calculating a standard deviation  the extra precision may be critical   On the other hand  in some cases not even double is going to give you enough precision    And beware of the trap of expecting float and double to give you an exact representation   They won t and they can t      There is a branch of mathematics called Numerical Analysis that deals with the effects of rounding error  etc in practical numerical calculations   It used to be a standard part of computer science courses     back in the 1970 s     Deciding between Double versus Float  For the Double versus Float case  the issues of precision and range are the same as for double versus float  but the relative performance measures will be slightly different      A Double  on a 32 bit machine  typically takes 16 bytes   4 bytes for the reference  compared with 12   4 bytes for a Float   Compare this to 8 bytes versus 4 bytes for the double versus float case   So the ratio is 5 to 4 versus 2 to 1  Arithmetic involving Double and Float typically involves dereferencing the pointer and creating a new object to hold the result  depending on the circumstances    These extra overheads also affect the ratios in favor of the Double case      Correctness  Having said all that  the most important thing is correctness  and this typically means getting the most accurate answer   And even if accuracy is not critical  it is usually not wrong to be  too accurate    So  the simple  rule of thumb  is to use double in preference to float  UNLESS there is an overriding performance requirement  AND you have solid evidence that using float will make a difference with respect to that requirement

[java] What exactly does Double mean in java?

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