I am a beginner in Java and I am having a problem sorting String. I know using Collections.sort it will sort String with case-sensitive by default but the uppercase ones always come in the front because it always compares the ASCII values.
If I want to keep lowercase String in front of uppercase ones, is there a clean way to implement it in Java using Collections.sort?
For example, to sort "java Python ruby C" into "java ruby C Python".
Thanks in advance.
You should implement your own Comparator to define such an ordering:
Collections.sort(list, new Comparator<String>() {
@Override
public int compare(String s1, String s2) {
if (/* s1 is lower case and s2 is upper case */) {
return 1;
}
if (/* s1 is upper case and s2 is lower case */) {
return -1;
}
return s1.compareTo(s2);
}
});
Of course you can use a Comparator .Use Collections.sort(List<String> x,Comparator comp)
This is achieved by creating a Comparator that will impelemt the compare method.
Here is example of using AgeComparator:
import java.util.Comparator;
public class HeightComparator implements Comparator<Object> {
@Override
public int compare(Object o1, Object o2) {
int p1 = ((Person)o1).height;
int p2 = ((Person)o2).height;
return p1 - p2;
}
}
Now all that left is to pass our custom comparator with the collection we want to compare.
Collections.sort(peoples, new AgeComparator())
More on Comparators and Comparable can be read HERE.
arshajii's answer is solid. Here're the two minor conditional statements:
Collections.sort(list, new Comparator<String>() {
@Override
public int compare(String s1, String s2) {
if (s1.toLowerCase().equals(s1) && s2.toUpperCase().equals(s2)) {
return 1;
}
if (s1.toUpperCase().equals(s1) && s2.toLowerCase().equals(s2)) {
return -1;
}
return s1.compareTo(s2);
}
};
