CODEWITHSUNDEEP
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daverocks
daverocks

Reputation: 2353

Integer or double return value

I have an Integer value been passed in and then it is divided by 100, so result could either be an int or double so not sure if cast it or not.

public void setWavelength(Integer value) {
    this.wavelength = value;
}

then value divided by 100

pluggable.setWavelength(entry.getPluggableInvWavelength()/100);

So not sure how to cast this value/object

Upvotes: 4

Views: 4621

Answers (4)

Peter Lawrey
Peter Lawrey

Reputation: 533530

if entry.getPluggableInvWavelength() returnsd an int the results of /100 will also be an int

If you have to have a double result, then you must store a double result.

double wavelength;

public void setWavelength(double value) {
    this.wavelength = value;
}  

pluggable.setWavelength(entry.getPluggableInvWavelength()/100.0);

Dividing by 100.0 is all you need to have a double result with 2 decimal places.

Upvotes: 0

Ralph
Ralph

Reputation: 120811

If you divide an integer (int) by an other integer (int) the result will be an integer (int) again. -- More details: 15.17 Multiplicative Operators

You need to mark one or both as double

//cast the divisor entry.getPluggableInvWavelength() to double
pluggable.setWavelength( ((double) entry.getPluggableInvWavelength()) /100);

or

//make the constant quotient a double
pluggable.setWavelength(entry.getPluggableInvWavelength() /100.0);

Pay attention to the fact, that java.lang.Integer is a immutable wrapper type and not an int! - In fact you can not calculate with java.lang.Integer, but since Java 1.5 the compiler will convert int to Integer and back automatically (auto boxing and auto unboxing). But in general it is better to understand the difference and use Integer only if you real need objects (and not numbers to calculate).

Upvotes: 4

Oliver Charlesworth
Oliver Charlesworth

Reputation: 272517

If you divide an int by an int, you always get an int. If you want a float or a double (because you need to represent fractional parts of the result), then you'll need to cast one or both inputs:

int a = 3;
int b = 4;

int    c1 = a / b;                  // Equals 0
double c2 = a / b;                  // Still equals 0
double c3 = (double)a / (double)b;  // Equals 0.75

Upvotes: 1

Bozho
Bozho

Reputation: 597114

If waveLength is double, then have:

entry.getPluggableWavelength() / 100d;

d means that the number is treated as double, and hence the division result is double.

Upvotes: 2

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