Cast Double to Integer in Java

Question

Any way to cast java lang Double to java lang Integer    It throws an exception       java lang ClassCastException  java lang Double incompatible with java lang Integer

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Memory efficient  as it will share the already created instance of Double   Double valueOf Math floor 54644546464 60 60 24 365   intValue

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Double and Integer are wrapper classes for Java primitives for double and int respectively  You can cast between those  but you will lose the floating point  That is  5 4 casted to an int will be 5  If you cast it back  it will be 5 0

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You can do that by using  Narrowing or Explicit type conversion   double   long   int  I hope it will work   double d   100 04  long l    long d     Explicit type casting required int i    int l        Explicit type casting required   PS  It will give 0 as double has all the decimal values and nothing on the left side  In case of 0 58  it will narrow it down to 0  But for others it will do the magic

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double a   13 34  int b    int  a   System out println b     prints 13

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Simply use the intValue method of Double  Double initialValue   7 12  int finalValue   initialValue intValue

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You need to explicitly get the int value using method intValue   like this   Double d   5 25  Integer i   d intValue       i becomes 5   Or   double d   5 25  int i    int  d

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I think it s impossible to understand the other answers without covering the pitfalls and reasoning behind it   You cannot directly cast an Integer to a Double object  Also Double and Integer are immutable objects  so you cannot modify them in any way    Each numeric class has a primitive alternative  Double vs double  Integer vs int        Note that these primitives start with a lowercase character  e g  int   That tells us that they aren t classes objects  Which also means that they don t have methods  By contrast  the classes  e g  Integer  act like boxes wrappers around these primitives  which makes it possible to use them like objects   Strategy   To convert a Double to an Integer you would need to follow this strategy    Convert the Double object to a primitive double      unboxing   Convert the primitive double to a primitive int      casting   Convert the primitive int back to an Integer object      boxing     In code      starting point Double myDouble   Double valueOf 10 0       step 1  unboxing double dbl   myDouble doubleValue        step 2  casting int intgr    int  dbl      step 3  boxing Integer val   Integer valueOf intgr     Actually there is a shortcut  You can unbox immediately from a Double straight to a primitive int  That way  you can skip step 2 entirely   Double myDouble   Double valueOf 10 0   Integer val   Integer valueOf myDouble intValue        the simple way   Pitfalls   However  there are a lot of things that are not covered in the code above  The code-above is not null-safe   Double myDouble   null  Integer val   Integer valueOf myDouble intValue        will throw a NullPointerException     a null-safe solution  Integer val    myDouble    null   null   Integer valueOf myDouble intValue       Now it works fine for most values  However integers have a very small range  min max value  compared to a Double  On top of that  doubles can also hold  special values   that integers cannot    1 0    infinity  -1 0   -infinity 0 0   undefined  NaN    So  depending on the application  you may want to add some filtering to avoid nasty Exceptions   Then  the next shortcoming is the rounding strategy  By default Java will always round down  Rounding down makes perfect sense in all programming languages  Basically Java is just throwing away some of the bytes  In financial applications you will surely want to use half-up rounding  e g    round 0 5    1 and round 0 4    0       null-safe and with better rounding long rounded    myDouble    null   0L  Math round myDouble doubleValue     Integer val   Integer valueOf rounded     Auto- un boxing  You could be tempted to use auto- un boxing in this  but I wouldn t  If you re already stuck now  then the next examples will not be that obvious neither  If you don t understand the inner workings of auto- un boxing then please don t use it   Integer val1   10     works Integer val2   10 0     doesn t work  Double val3   10     doesn t work Double val4   10 0     works  Double val5   null   double val6   val5     doesn t work  throws a NullPointerException    I guess the following shouldn t be a surprise  But if it is  then you may want to read some article about casting in Java   double val7    double  10     works Double val8    Double  Integer valueOf 10      doesn t work Integer val9    Integer  9     pure nonsense   Prefer valueOf   Also  don t be tempted to use new Integer   constructor  as some other answers propose   The valueOf   methods are better because they use caching  It s a good habit to use these methods  because from time to time they will save you some memory   long rounded    myDouble    null   0L  Math round myDouble doubleValue     Integer val   new Integer rounded      waste of memory

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A Double is not an Integer  so the cast won t work   Note the difference between the Double class and the double primitive   Also note that a Double is a Number  so it has the method intValue  which you can use to get the value as a primitive int

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It s worked for me  Try this   double od   Double parseDouble  1 15    int oi    int  od

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I see three possibilities  The first two cut off the digits  the last one rounds to the nearest Integer   double d   9 5  int i    int d    i   9  Double D   9 5  int i   Integer valueOf D intValue       i   9  double d   9 5  Long L   Math round d   int i   Integer valueOf L intValue       i   10

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Use the doubleNumber intValue    method

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Double d   100 00  Integer i   d intValue      One should also add that it works with autoboxing   Otherwise  you get an int  primitive  and then can get an Integer from there   Integer i   new Integer d intValue

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Try this one  double doubleValue   6 5 Double doubleObj   new Double doubleValue  int intResult   doubleObj intValue

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Simply do it this way     Double d   13 5578  int i   d intValue    System out println i

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Alternatively  one can first cast to primitive double  then cast to int  letting it be autoboxed to Integer  Double d   20 3  Integer i    int   double  d    20   To obtain primitive  int i2    int   double  d

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Call intValue   on your Double object

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Like this     Double foo   123 456  Integer bar   foo intValue

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Indeed  the simplest way is to use intValue    However  this merely returns the integer part  it does not do any rounding  If you want the Integer nearest to the Double value  you ll need to do this   Integer integer   Integer valueOf  int  Math round myDouble       And don t forget the null case   Integer integer   myDouble    null   null   Integer valueOf  int  Math round myDouble       Math round   handles odd duck cases  like infinity and NaN  with relative grace

[java] Cast Double to Integer in Java

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