How convert a long to int in Java vs. swift?

Question

I have try to convert this code in Java to swift 2.0

long checksumValue = 4253726258L;
int liCrc32 = (int)checksumValue;
System.out.println("liCrc32" + liCrc32)

LiCrc32 is equal to -41241038

My swift version

let int64: Int64 = 4253726258
let a:Int = Int(int64)

a returns me 4253726258

What i don't understand why in Java the value is negative?

Answer 1

From the Swift documentation

Int

In most cases, you don’t need to pick a specific size of integer to use in your code. Swift provides an additional integer type, Int, which has the same size as the current platform’s native word size:

• On a 32-bit platform, Int is the same size as Int32.

• On a 64-bit platform, Int is the same size as Int64.

Unless you need to work with a specific size of integer, always use Int for integer values in your code. This aids code consistency and interoperability. Even on 32-bit platforms, Int can store any value between -2,147,483,648 and 2,147,483,647, and is large enough for many integer ranges.

Java's int, on the other hand, is always 4 bytes.

The integral types are byte, short, int, and long, whose values are 8-bit, 16-bit, 32-bit and 64-bit signed two's-complement integers, respectively, [...]

Casting from a long to an int causes a narrowing primitive conversion

A narrowing primitive conversion may lose information about the overall magnitude of a numeric value and may also lose precision and range.