After knowing primitive data types and Java rules of Data Type Casting (Type Conversion), let us cast double to byte. The byte data type takes 1 byte of memory and double takes 8 bytes of memory. Assigning 8 bytes of memory to 1 byte of memory requires explicit casting. Moreover, double takes a mantissa (value after decimal point) but byte does not (byte is whole number). In explicit casting, the mantissa part is truncated.
The left-side value can be assigned to any right-side value and is done implicitly. The reverse like double to byte requires explicit casting.
Examples of implicit casting
int x = 10; // 4 bytes
double y = x; // 4 bytes to 8 bytesbyte x = 10; // 1 byte
int y = x; // 1 byte to 4 bytes
Following program explains double to byte explicit casting. Observe, the Java style where a double is assigned to a byte.
public class Conversions
{
public static void main(String args[])
{
double d1 = 10.5; // 8 bytesb1
// byte b1 = d1; // error as 8 bytes to 1 byte
byte b1 = (byte) d1; // 8 bytes double type explicitly casted to 1 byte value byte
System.out.println("\ndouble value: " + d1); // prints 10.5
System.out.println("Converted byte value: " + b1 ); // prints 10; observe 0.5 is lost
}
}
Output screenshot of double to byte Java
byte b1 = d1;
The above statement raises a compilation error" of possible loss of precision".
byte b1 = (byte) d1;
The double d1 is explicitly type casted to byte b1. Observe, the syntax of explicit casting. On both sides, it should be byte only. When casted, the precision of 0.5 is lost (for this reason only, the compiler raises error). This is known as data truncation.
