List sorting

In this chapter you will learn:

How to Sort a list
Sort elements of ArrayList
Sort elements of Vector
Sort ArrayList in descending order using comparator

Sort a list

List is a sequence of elements. We can search a list with a default comparator or we can use a specified comparator.

static<T extends Comparable<? super T>>void sort(List<T> list)
Sorts the specified list into ascending order, according to the natural ordering of its elements.
static<T> void sort(List<T> list, Comparator<? super T> c)
Sorts the specified list according to the order induced by the specified comparator.

import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedList;
/*j  a va  2  s . c o  m*/
public class Main {
  public static void main(String args[]) {
    LinkedList<Integer> ll = new LinkedList<Integer>();
    ll.add(-8);
    ll.add(20);
    ll.add(-20);
    ll.add(8);

    Comparator<Integer> r = Collections.reverseOrder();

    Collections.sort(ll, r);

    System.out.print("List sorted in reverse: ");
    System.out.print(ll);
  }
}

The output:

Sort elements of ArrayList

In the following code we sort an ArrayList.

import java.util.ArrayList;
import java.util.Collections;
/* j  a  v  a  2 s  . c  om*/
public class Main {
  public static void main(String[] args) {
    ArrayList arrayList = new ArrayList();
    arrayList.add("1");
    arrayList.add("2");
    arrayList.add("3");
    arrayList.add("4");
    arrayList.add("java2s.com");
    Collections.sort(arrayList);

    System.out.println(arrayList);
  }
}

The output:

Sort elements of Vector

import java.util.Vector;
import java.util.Collections;
/*from  j  a  v  a 2 s . c om*/
public class Main {
  public static void main(String[] args) {
    Vector v = new Vector();
    v.add("1");
    v.add("3");
    v.add("5");
    v.add("2");
    v.add("java2s .com ");
    Collections.sort(v);

    System.out.println(v);
  }
}

The output:

Sort ArrayList in descending order using comparator

The following code sorts ArrayList in descending order. The control over descending order or ascending order is through different comparators.

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
/*from  j  a  v a 2  s. co m*/
public class Main {
  public static void main(String[] args) {
    ArrayList arrayList = new ArrayList();
    arrayList.add("A");
    arrayList.add("B");
    arrayList.add("C");
    arrayList.add("D");
    arrayList.add("java2s.com");
    Comparator comparator = Collections.reverseOrder();
    System.out.println("Before: " + arrayList);
    Collections.sort(arrayList, comparator);
    System.out.println("After sorting: " + arrayList);
  }
}