Core Java - Type Casting

Typecasting

• Converting one type to another type is called typecasting.
• Conversion is done from primitive to primitive or nonprimitive to nonprimitive.

Example

int i = 10;
double d = (double) i;
SOP(i); // 10
SOP(d); // 10.0
int j = (int) 102.56;
SOP(j); // 102


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• Boolean type can't be casted.
• If we convert smaller to bigger type, it is called widening or explicit type casting.
• If we convert bigger to a smaller type, it is called narrowing or implicit type casting.
• Widening is implicit or automatic.
• Narrowing is explicit.
• In widening there is no loss of data.
• In narrowing, loss of data or loss of precision may take place.

8 primitive types, their size and default values

Type	Size	Default value
byte	1 byte	0
short	2 byte	0
int	4 byte	0
long	8 byte	0
float	4 byte	0.0f
double	8 bye	0.0d
char	2 byte	'\u0000'
boolean	Not defined	false

public static void main(String[] arg){
m1('a');
m1(34.562); // compile time error
}
static void m1(int a){
System.out.print(a);
}


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class J{
public static void main(String[] arg){
m1(10); // calls int
m1('a'); // calls int
m1(23.45); // calls double
}
static void m1(int a){
System.out.print("m1(int a)");
}
static void m1(double d){
System.out.print("m1() double");
}
}


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static double m1(){
return 'a';
}


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In the above example, return type is double, but we are using char as a return type. It is possible because of auto widening. Smaller type is a covariant return type for a bigger type.