Convert Long into Integer

Question

How to convert a Long value into an Integer value in Java

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The best simple way of doing so is   public static int safeLongToInt  long longNumber                  if   longNumber  lt  Integer MIN VALUE    longNumber  gt  Integer MAX VALUE                          throw new IllegalArgumentException  longNumber     cannot be cast to int without changing its value                        return  int  longNumber

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In Java 8 you can use Math toIntExact  If you want to handle null values  use  Integer intVal   longVal    null   null   Math toIntExact longVal    Good thing about this method is that it throws an ArithmeticException if the argument  long  overflows an int

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For non-null values   Integer intValue   myLong intValue

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In addition to  Thilo s accepted answer  Math toIntExact works also great in Optional method chaining  despite it accepts only an int as an argument Long coolLong   null  Integer coolInt   Optional ofNullable coolLong  map Math  toIntExact  orElse 0     yields 0

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Assuming not null  longVal  Integer intVal     Number longVal  intValue      It works for example y you get an Object that can be an Integer or a Long  I know that is ugly  but it happens

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try this  Int i   Long valueOf L    L  Long Value

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Integer i   theLong    null   theLong intValue     null    or if you don t need to worry about null      auto-unboxing does not go from Long to int directly  so Integer i    int   long  theLong    And in both situations  you might run into overflows  because a Long can store a wider range than an Integer    Java 8 has a helper method that checks for overflow  you get an exception in that case    Integer i   theLong    null   null   Math toIntExact theLong

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long visitors  1000   int convVisitors   int visitors

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In java  there is a rigorous way to convert a long to int  not only lnog can convert into int any type of class extends Number can convert to other Number type in general here I will show you how to convert a long to int other type vice versa   Long l   1234567L  int i   org springframework util NumberUtils convertNumberToTargetClass l  Integer class

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If you are using Java 8 Do it as below      import static java lang Math toIntExact       public class DateFormatSampleCode           public static void main String   args                long longValue   1223321L              int longTointValue   toIntExact longValue               System out println longTointValue

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If you care to check for overflows and have Guava handy  there is Ints checkedCast     int theInt   Ints checkedCast theLong     The implementation is dead simple  and throws IllegalArgumentException on overflow   public static int checkedCast long value      int result    int  value    checkArgument result    value   Out of range   s   value     return result

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Here are three ways to do it   Long l   123L  Integer correctButComplicated   Integer valueOf l intValue     Integer withBoxing   l intValue    Integer terrible    int   long  l    All three versions generate almost identical byte code    0  ldc2 w  lt Long 123 gt   17   3  invokestatic java lang Long valueOf long    java lang Long  19   6  astore 1  l      first  7  aload 1  l   8  invokevirtual java lang Long intValue     int  25  11  invokestatic java lang Integer valueOf int    java lang Integer  29  14  astore 2  correctButComplicated     second 15  aload 1  l  16  invokevirtual java lang Long intValue     int  25  19  invokestatic java lang Integer valueOf int    java lang Integer  29  22  astore 3  withBoxing     third 23  aload 1  l     here s the difference  24  invokevirtual java lang Long longValue     long  34  27  l2i 28  invokestatic java lang Integer valueOf int    java lang Integer  29  31  astore 4  terrible

User · Answer

Using toIntExact long value  returns the value of the long argument  throwing an exception if the value overflows an int  it will work only API level 24 or above   int id   Math toIntExact longId

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You ll need to type cast it   long i   100L  int k    int  i    Bear in mind that a long has a bigger range than an int so you might lose data   If you are talking about the boxed types  then read the documentation

[java] Convert Long into Integer

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