Type Conversion and Casting

Assigning value of one type to variable of another type is known as conversion.

In java we have two types of conversions.

1. Implicit type conversion.
2. Explicit type conversion.

1. implicit type conversion

Java automatically converts from one type to another  if it satisfy the following conditions.

1 Both types are compatible with each other.

2 The size of destination type is more than the source type.

This is also known as “Widening Conversion”.

Example

int i = 3;                                   int i=5;//size of int is 32

double f;                                  long d;//size of long is 64

f = i;                                        d=I;    

Example program

class TypeConversion
{
    public static void main(String arg[])
    {
        byte b = 50;
        short s = 4125;
        int i = 800000;
        long l = 107343L;       
        s = b;    
        i = s;   
        l = i;   
        float f = 25.0f;
        double d = 327.98;
        f = i;
        d = f;
        System.out.println("b = " + b );   
        System.out.println("s = " + s );   
        System.out.println("i = " + i );   
        System.out.println("l = " + l );   
        System.out.println("d = " + d );   
        System.out.println("f = " + f );  
    }
}

2. Explicit type conversion

If we want to convert two types which are incompatible or if the size of destination type is less than the size of source type, then we must do the conversion explicitly.

This process is also called as “type casting”. This is also called as Narrowing conversion .

Explicit type cast is requires to Narrowing conversion to inform the compiler that you are aware of the possible loss of precision.

Syntax

newValue = (typecast)value;

Example

double f = 3.5;

int i;

 i = (int)f; // it cast double value 3.5 to int 3.

Example program

class DatatypeCasting
{
    public static void main(String arg[])
    {
        byte b;
        int i = 81;
        double d = 323.142;
        float f = 72.38f;
        char c = 'A';
       
        c = (char) i;
        System.out.println("i = " + i + " c = " + c);
       
        i = (int) d; 
        System.out.println("d = " + d + " i = " + i); 
       
        i = (int) f; 
        System.out.println("f = " + f + " i = " + i); 
       
        b = (byte) d;
        System.out.println("d = " + d + " b = " + b);
   
    }
}