Sorting
We can sort the elements of:
- String
objects
- Wrapper
class objects
- User-defined
class objects
|
Collections class provides static methods for sorting
the elements of collection.If collection elements are of Set type, we can use
TreeSet.But We cannot sort the elements of List.Collections class provides
methods for sorting the elements of List type elements.
|
Method
of Collections class for sorting List elements
|
public void
sort(List list): is
used to sort the elements of List.List elements must be of Comparable type.
|
Note: String class
and Wrapper classes implements the Comparable interface.So if you store the
objects of string or wrapper classes, it will be Comparable.
Example
of Sorting the elements of List that contains string objects
1. import java.util.*;
2. class TestSort1{
3. public static void main(String args[]){
4.
5. ArrayList<String> al=new ArrayList<String>();
6. al.add("Viru");
7. al.add("Saurav");
8. al.add("Mukesh");
9. al.add("Tahir");
10.
11. Collections.sort(al);
12. Iterator itr=al.iterator();
13. while(itr.hasNext()){
14. System.out.println(itr.next());
15. }
16. }
17. }
Output:Mukesh
Saurav
Tahir
Viru
Example
of Sorting the elements of List that contains Wrapper class objects
1. import java.util.*;
2. class TestSort2{
3. public static void main(String args[]){
4.
5. ArrayList al=new ArrayList();
6. al.add(Integer.valueOf(201));
7. al.add(Integer.valueOf(101));
8. al.add(230);//internally will be converted into objects as Integer.valueOf(230)
9.
10. Collections.sort(al);
11.
12. Iterator itr=al.iterator();
13. while(itr.hasNext()){
14. System.out.println(itr.next());
15. }
16. }
17. }
Output:101
201
230
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