In this example we shall show you how to sort a Vector using a Comparator. The Collections API provides methods to get a Comparator and use it to sort a Vector. To sort a Vector using a Comparator one should perform the following steps:
- Create a new Vector.
- Populate the vector with elements, using
add(Object o)API method of Vector. - Invoke
reverseOrder()API method of Collections to get a Comparator that imposes the reverse of the natural ordering on the vector’s elements. - Invoke
sort(List list, Comparator c)API method of Collections in order to sort the vector elements using the comparator. The vector’s elements will be sorted according to the comparator.
We can get the vector’s elements before and after sorting to check how they are sorted. Before sorting the vector elements are sorted by insertion order,
as described in the code snippet below.
package com.javacodegeeks.snippets.core;
import java.util.Vector;
import java.util.Collections;
import java.util.Comparator;
public class SortArrayListComparator {
public static void main(String[] args) {
// Create a Vector and populate it with elements
Vector vector = new Vector();
vector.add("element_1");
vector.add("element_3");
vector.add("element_5");
vector.add("element_2");
vector.add("element_4");
// Vector implementation maintains the insertion order for its elements
System.out.println("Elements in Vector prior sorting :");
for(int i=0; i < vector.size(); i++)
System.out.println(vector.get(i));
/*
To get a comparator that imposes reverse order on a Collection's elements
we can use static Comparator reverseOrder() operation of Collections class
*/
Comparator comparator = Collections.reverseOrder();
// Using Collection.sort(List list, Comparator c) static operation we can sort Vector elements using a Comparator
Collections.sort(vector,comparator);
System.out.println("Elements in Vector after sorting :");
for(int i=0; i < vector.size(); i++)
System.out.println(vector.get(i));
}
}
Output:
Elements in Vector prior sorting :
element_1
element_3
element_5
element_2
element_4
Elements in Vector after sorting :
element_5
element_4
element_3
element_2
element_1
This was an example of how to sort a Vector using a Comparator in Java.
