Safely casting long to int in Java

Question

What s the most idiomatic way in Java to verify that a cast from long to int does not lose any information   This is my current implementation   public static int safeLongToInt long l        int i    int l      if   long i    l            throw new IllegalArgumentException l     cannot be cast to int without changing its value               return i

User · Accepted Answer

A new method has been added with Java 8 to do just that    import static java lang Math toIntExact   long foo   10L  int bar   toIntExact foo     Will throw an ArithmeticException in case of overflow    See  Math toIntExact long    Several other overflow safe methods have been added to Java 8  They end with exact    Examples     Math incrementExact long  Math subtractExact long  long  Math decrementExact long  Math negateExact long   Math subtractExact int  int

User · Answer

I claim that the obvious way to see whether casting a value changed the value would be to cast and check the result  I would  however  remove the unnecessary cast when comparing  I m also not too keen on one letter variable names  exception x and y  but not when they mean row and column  sometimes respectively     public static int intValue long value        int valueInt    int value      if  valueInt    value            throw new IllegalArgumentException               The long value   value   is not within range of the int type                       return valueInt      However  really I would want to avoid this conversion if at all possible  Obviously sometimes it s not possible  but in those cases IllegalArgumentException is almost certainly the wrong exception to be throwing as far as client code is concerned

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With BigDecimal   long aLong        int anInt   new BigDecimal aLong  intValueExact       throws ArithmeticException                                                       if outside bounds

User · Answer

One other solution can be    public int longToInt Long longVariable        try                return Integer valueOf longVariable toString                catch IllegalArgumentException e                    Log e e printstackstrace                    I have tried this for cases where the client is doing a POST and the server DB understands only Integers while the client has a Long

User · Answer

DONT  This is not a solution   My first approach was   public int longToInt long theLongOne      return Long valueOf theLongOne  intValue        But that merely just casts the long to an int  potentially creating new Long instances or retrieving them from the Long pool     The drawbacks   Long valueOf creates a new Long instance if the number is not within Long s pool range  -128  127   The intValue implementation does nothing more than   return  int value     So this can be considered even worse than just casting the long to int

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With Google Guava s Ints class  your method can be changed to   public static int safeLongToInt long l        return Ints checkedCast l       From the linked docs      checkedCast      public static int checkedCast long value       Returns the int value that is equal to value  if possible       Parameters    value - any value in the range of the int type      Returns    the int value that equals value      Throws    IllegalArgumentException - if value is greater than Integer MAX VALUE or less than Integer MIN VALUE   Incidentally  you don t need the safeLongToInt wrapper  unless you want to leave it in place for changing out the functionality without extensive refactoring of course

User · Answer

here is a solution  in case you don t care about value in case it is bigger then needed     public static int safeLongToInt long l        return  int  Math max Math min Integer MAX VALUE  l   Integer MIN VALUE

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Java integer types are represented as signed  With an input between 231 and 232  or -231 and -232  the cast would succeed but your test would fail    What to check for is whether all of the high bits of the long are all the same   public static final long LONG HIGH BITS   0xFFFFFFFF80000000L  public static int safeLongToInt long l        if   l  amp  LONG HIGH BITS     0     l  amp  LONG HIGH BITS     LONG HIGH BITS            return  int  l        else           throw new IllegalArgumentException

User · Answer

I think I d do it as simply as   public static int safeLongToInt long l        if  l  lt  Integer MIN VALUE    l  gt  Integer MAX VALUE            throw new IllegalArgumentException              l     cannot be cast to int without changing its value               return  int  l      I think that expresses the intent more clearly than the repeated casting    but it s somewhat subjective   Note of potential interest - in C  it would just be   return checked   int  l

User · Answer

int   longType   0    but Long can not exceed the maximum

[java] Safely casting long to int in Java

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