Explaining Java casting

To discuss casting properly, we need to explain both the widening and narrowing of Java’s primitive data types. With this in mind, it is helpful to remember the sizes of the primitive data types in bytes. Table 3.3 represents this information:

Table 3.3 – The sizes of Java’s primitive types

The preceding table presents the sizes in bytes of Java’s various primitive data types. This will help us as we discuss both widening and narrowing.

Widening

Widening is done automatically; in other words, a cast is not needed. As the promotion is done in the background, widening is also known as implicit promotion. With Table 3.3 in mind, the widening rules are as follows:

byte → short/char → int → long → float → double

Given the sizes from Table 3.3, most of these rules should make sense. For example, a byte can automatically fit into a short because 1 byte fits into...