Why compiler doesn't give error when we assign Integer(object) to int(primitive)?
int i;
Integer ii = new Integer(5);
i = ii;//no compilation error.
And this is the case with all other types(byte-Byte, float-Float)..
What is the reason? Am i missing something here?
It's called autoboxing/unboxing.
As of Java 1.5, the compiler automatically "boxes" primitives into their corresponding class (eg int and Integer, double and Double etc), and un-boxes as required.
See this page in the documentation for more details.
Java 5 and newer are able to perform autoboxing. The compiler will implicitly transform your code into:
int i;
Integer ii = new Integer(5);
i = ii.intValue();
Java SE 5.0 introduced autoboxing as a new feature. You can find more information in the Java documentation. http://docs.oracle.com/javase/1.5.0/docs/guide/language/autoboxing.html
i = ii;//no compilation error.
Because this is called autounboxing. When you assign object to primitive variable, value from object is taken out and assigned to primitive. this process is called autounboxing.
Vice versa is Autoboxing.
This is called "autoboxing/unboxing". The primitive types like int are automatically converted to classes like Integer and vice-versa when it is needed.
