I am able to compare Strings fine, but would like to know how I can rank floating point numbers?
getChange() returns a String. I want to be able to sort descending. How can I do this?
UPDATE:
package org.stocktwits.helper;
import java.util.Comparator;
import org.stocktwits.model.Quote;
public class ChangeComparator implements Comparator<Quote>
{
public int compare(Quote o1, Quote o2) {
float change1 = Float.valueOf(o1.getChange());
float change2 = Float.valueOf(o2.getChange());
if (change1 < change2) return -1;
if (change1 == change2) return 0; // Fails on NaN however, not sure what you want
if (change2 > change2) return 1;
}
}
I am getting the compile time error:
This method must return a result of type int ChangeComparator.java
How about this:
public class ChangeComparator implements Comparator<Quote>
{
public int compare(Quote o1, Quote o2) {
Float change1 = Float.valueOf(o1.getChange());
Float change2 = Float.valueOf(o2.getChange());
return change1.compareTo(change2);
}
}
Note that Java 1.4 introduced Float#compare(float, float)
(and an equivalent in Double
), which can be pretty much used directly:
public class ChangeComparator implements Comparator<Quote>
{
public int compare(Quote o1, Quote o2) {
return Float.compare(o1.getChange(), o2.getChange());
}
}
(After editing, I notice that @BorislavGizdov has mentioned this in his answer already.)
Also worth noting that Java 8 Comparator#comparing(...)
and Comparator#comparingDouble(...)
provide a straightforward way of constructing these comparators directly.
Comparator<Quote> changeComparator = Comparator.comparing(Quote::getChange);
Will compare using boxed Float
values.
Comparator<Quote> changeComparator = Comparator.comparingDouble(Quote::getChange);
Will compare using float
values promoted to double
values.
Given that there is no Comparator#comparingFloat(...)
, my preference would be to use the comparingDouble(...)
method, as this only involves primitive type conversion, rather than boxing.