I wrote a function in Java and I want this function to return multiple values. Except use of array and structure, is there a way to return multiple values?
My code:
String query40 = "SELECT Good_Name,Quantity,Price from Tbl1 where Good_ID="+x;
Cursor c = db.rawQuery(query, null);
if (c!= null && c.moveToFirst())
{
GoodNameShow = c.getString(0);
QuantityShow = c.getLong(1);
GoodUnitPriceShow = c.getLong(2);
return GoodNameShow,QuantityShow ,GoodUnitPriceShow ;
}
In Java, when you want a function to return multiple values, you must
In your case, you clearly need to define a class Show which could have fields name, quantity and price :
public class Show {
private String name;
private int price;
// add other fields, constructor and accessors
}
then change your function to
public Show test(){
...
return new Show(GoodNameShow,QuantityShow ,GoodUnitPriceShow) ;
Collection.sort is bad style ? You can't make efficient code if you try to make it understandable by people who don't know the most basic facts of the language. If somebody doesn't know that a received object can be changed by a method, then he must learn before being involved in a professional team.x,y = y,x), but multiple return values is very useful (x,y = function(params)). Forcing a wrapping object to be returned (often by "clean" declarations similar to class Pair<A,B>)has a penalty under very many tight calls, and passing an object to hold return values is horribly messy with no compiler guarantee that the fields are filled.One quick and ugly approach I encountered a few times (even in java library itself) is to return your values as Object[] and then unpack using casting.
e.g.
public Object[] myfunc() {
String name = "...";
Integer quantity = 5
Float price = 3.14
return new Object[] { name, quantity, price };
Then, it is used like this:
Object[] output = myfunc();
String name = (String) output[0];
Integer quantity = (Integer) output[1];
Float price = (Float) output[2];
Embedding the values in a dedicated object is much cleaner, but I leave it here anyway.
I have developed a very basic approach to deal with this kind of situation.
I have used a logic of seperator in Strings.
For example if you need to return in the same function 1. int value 2. double value 3. String value
you could use a separator string
For example ",.," this kind of string would not generally appear anywhere.
You could return a String consisting of all values separated by this separator "< int value >,.,< double value >,.,< String value >"
and convert into equivalent types where the function has been called by using String.split(separtor)[index]
Refer the following code for explanation -
separator used =",.,"
public class TestMultipleReturns{
public static void main(String args[]){
String result = getMultipleValues();
int intval = Integer.parseInt(result.split(",.,")[0]);
double doubleval = Double.parseDouble(result.split(",.,")[1]);
String strval = result.split(",.,")[2];
}
public static String getMultipleValues(){
int intval = 231;//some int value
double doubleval = 3.14;//some double val
String strval = "hello";//some String val
return(intval+",.,"+doubleval+",.,"+strval);
}
}
This approach can be used as a shortcut when you do not want to increase number of classes for only function returns
It depends on situation to situation which approach to take.
StringBuilder, Strings) which are far more expensive than a single instance of a utility class. The effort of retrieving the values is unjustifiable large, requires unnecessary code and has a noticeable impact on the performance. As you already noticed, the separator must not appear in the string and that is usally an unjustifiable assumption.
goodNameShoworgoodUnitPriceShow).