Java | Type Conversions

05 min read

Type Conversions:

Type conversions are the conversion of data types from one form to another. There are several types of conversions which will be seen below,

1. Widening Primitive Conversion: (Implicit Conversion)

Possible only if the

  • 2 types are compatible. (eg) double to byte - not possible
  • Destination type is larger than the source type.

No automatic type conversion from numeric types to boolean. There are totally 19 widening conversions on primitive types.

  • byte to short, int, long, float or double
  • short to int, long, float or double
  • int to long, float or double
  • long to float or double
  • float to double

A widening conversion does not lose information.

2. Narrowing Primitive Conversions: (Explicit Conversion)

  • Done when automatic type conversion is not possible.
  • Uses typecasting.

(eg) int a = 120;

byte b = (byte)a;

System.out.println(b) -> 120

For any value assigned to a byte variable, modulo division by 256 will be done and the resulting remainder will be assigned to the byte variable. Therefore, 120 % 256 =120.

3. Truncation:

A conversion which occurs when a floating-point value is assigned to an integer type.

(eg) int I = 25.25;       i-> 25

byte b = (byte)323.142;    ->  67 (because the fractional part is lost and also the value is reduced module 256)

4.Widening and Narrowing Conversion:

byte to char

First, the byte is converted into an int via widening primitive conversion and then the resulting int is converted to a char by narrowing primitive conversion.

(eg) byte b = (byte)130;

char cc = (char)b;  ->  here 'b' is converted to 'int' by widening conversion; however 'int' has to be converted to 'char' by narrowing conversion.

5. Automatic type expressions:

Sometimes in an expression, the precision required of an intermediate value will exceed the range of either operand.

(eg) byte b=50, a=40, c=100;

int d=a*b/c;  //exceeds the range of byte.

For this reason, whenever evaluating an expression, Java automatically promotes each byte, short or char operand to int.

a*b is performed using int and not bytes & hence it is legal.

But these automatic promotions may sometimes cause compile-time errors.

(eg) byte b = 50;

b = b*2;  -> error because when the expression is evaluated, the result has already been promoted to int. So, int result cannot be assigned to a byte without typecasting.

byte b = 50;

b = (byte)(b*2);

 

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