Example Method Calls

Where there is no loss of information, or only a possible loss of precision, Java will automatically convert the value in a method call to what is required. When there is a possible loss of both precision and magnitude, Java requires you to explicitly state that you want to go ahead with the conversion by using a type cast.

For example:

Point  A = new Point();

short  a = 93,    b = 92;
int    i = 12,    j = 13;
long   x =  0,    y = 44;
double u = 13.45, v = 99.2;

A.move( i, j );             // OK --- no conversion needed.
A.move( a, b );             // OK --- shorts converted to ints with no loss
A.move( a, j );             // OK --- short converted to int with no loss

A.move( x, y );             // NOT OK --- possible loss of 
                            // precision and magnitude.
A.move( (int)x, (int)y );   // OK --- type casts say to go ahead

A.move( i, v );             // NOT OK -- possible loss of 
                            // precision and magnitude (for v).
A.move( i, (int)v );        // OK --- type cast says to go ahead.

In making these decisions, it is only the type of the variable (or the expression) that is examined, NOT the particular value. For example, in the first method call marked NOT OK, the particular values could (in this case) be converted from long to int without loss of information. But for other values there would be total loss of information, so the call requires a type cast.

Also notice that the conversion is done on a parameter-by-parameter basis. In the third call, only the parameter a needed to be converted.