Why is Casting not transitive

Asked Feb 06 '18 at 16:47

Active Feb 06 '18 at 16:50

Viewed 85 times

Consider the following example in java (or c#):

 //doesn't work
 Object a = 5.2f;
 int b = (int)a; //java.lang.ClassCastException: java.base/java.lang.Float cannot be cast to java.base/java.lang.Integer

 //must first cast object to float, then can cast to integer
 Object a = 5.2f;
 int b = (int)(float)a;

I had always just assumed casting is transitive (A=B & B=C THEN A=C), however that obviously isn't the case.

Can someone explain exactly why this doesn't work?

edited Feb 06 '18 at 16:50

asked Feb 06 '18 at 16:47

NSjonas

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In this case you do not only cast but also auto-box to a Float object. – Henry Feb 06 '18 at 16:50
https://stackoverflow.com/questions/24332413/java-auto-boxing-and-casting – Murat Karagöz Feb 06 '18 at 16:51
Just in case you need to solve the specific problem, `int b = ((Number)a).intValue();` works for any numeric primitive type ([demo](https://ideone.com/L78ZvF)) – Sergey Kalinichenko Feb 06 '18 at 16:52
@dasblinkenlight just asking out of curiosity, thanks though – NSjonas Feb 06 '18 at 16:53
Skeets answer here is what I was looking for: https://stackoverflow.com/questions/27459780/cast-object-type-double-to-int/27459873#27459873 – NSjonas Feb 06 '18 at 16:57

Why is Casting not transitive

0 Answers0