CODEWITHSUNDEEP
javalistsorting
user3259071
user3259071

Reputation:

Sorting a list of strings

I was handed this assignment:

Complete the function void sort(List l) that sorts a list l that contains the strings "one","two","three","four" (although not necessarily in that order). You should declare a Comparator, and use this with the Collections.sort function. The comparator should use the comp function described above. The list l will be altered when it is sorted.

and the code I have already writen is this:

import java.util.*;

public class CW3 {

    private static HashMap < String, Integer > map = new HashMap < String, Integer > ();

    public CW3() {
        map.put("one", 1);
        map.put("two", 2);
        map.put("three", 3);
        map.put("four", 4);

        List listB = Arrays.asList("A", "B", "C");
    }

    public static void main(String[] args) {
        System.out.println(new CW3().comp("one", "two"));
        System.out.println(new CW3().comp("two", "one"));
        System.out.println(new CW3().comp("one", "one"));
    }

    int comp(String s1, String s2) {
        int i1 = map.get(s1);
        int i2 = map.get(s2);
        return (i1 < i2 ? -1 : (i1 == i2 ? 0 : 1));
    }

    void sort(List l) {
        Comparator c = new Comparator() {

            public int compare(Object o1, Object o2) {
                return 0; // FIXME change this so it calls comp
            }
        };
        // now sort l using the comparator c
        // FIXME complete this line
    }

Any ideas where to start? it says list so I would have to create a list but then how would I sort them?

Upvotes: 0

Views: 164

Answers (2)

Game Over
Game Over

Reputation: 6

you can use below compar method 

public class StepComparator implements Comparator<Step>{

@Override
public int compare(String so1, String s2) {

    if(map.get(s1)>map.get(s2)) return 1;

    return -1;
}

}

then you use this to sort them 

StepComparator  comparator = new  StepComparator();
Collections.sort(list,comparator);

Upvotes: 0

Warlord
Warlord

Reputation: 2826

What you need to do is to define the compare method. It should take two objects o1 and o2 as parameters and return

  • -1 when o1 < o2
  • 0 when o1 == o2
  • 1 when o1 > o2

Your Comparator uses this method as a basis to decide the order of the elements. Then you sort the list l by calling Collections.sort(l, c), where c is the Comparator you have defined.

Upvotes: 1

Related Questions