Sorting collection of String and StringBuffer in Java - GeeksforGeeks

09 Nov, 2020
Sorting a collection of objects can be done in two ways: 
By implementing Comparable (Natural Order) e.g. Strings are sorted ASCIIbetically. meaning B comes before A and 10 is before 2.
By implementing Comparator (Custom order) and it can be in any order.
Using Collections.sort() method of Collections utility class. 
Read more about Comparable and ComparatorFor sorted Collection we can use below collections: 
TreeSet
TreeMap
In case of String, sorting will be done automatically in natural order. 
Java
// Java program to sort String objects using TreeSetimport java.util.Set;import java.util.TreeSet; public class Test {    public static void main(String[] args)    {        Set<String> str = new TreeSet<String>();        str.add("Sohan");        str.add("Raja");        str.add("Harish");        str.add("Ram");        System.out.println(str);    }}
Output:  
[Harish, Raja, Ram, Sohan]

Java
// Java program to demonstrate that simple sorting// StringBuffer objects does work.import java.util.Set;import java.util.TreeSet; public class Test {     public static void main(String[] args)    {        Set<StringBuffer> str = new TreeSet<>();        str.add(new StringBuffer("Sohan"));        str.add(new StringBuffer("Raja"));        str.add(new StringBuffer("Harish"));        str.add(new StringBuffer("Ram"));        System.out.println(str);    }}
[Harish, Raja, Ram, Sohan]

String class implements Comparable interface whereas StringBuffer and StringBuilder classes do not implement Comparable interface. See below signatures of String, StringBuffer and StringBuilder classes: 
Java
public final class String    extends Object        implements Serializable,    Comparable, CharSequence
Java
public final class StringBuffer    extends Object        implements Serializable,    CharSequence
Java
public final class StringBuilder    extends Object        implements Serializable,    CharSequence
There are many ways of sorting StringBuffer, StringBuilder classes. Some of the ways are given below: 
By implementing Comparator interface
By converting StringBuffer to String using StringBuffer.toString() method
Java
// Java program to demonstrate sorting// of StringBuffer objects using Comparator// interface.import java.util.Comparator;import java.util.Set;import java.util.TreeSet; public class Test implements Comparator<StringBuffer> {    @Override public int compare(StringBuffer s1, StringBuffer s2)    {        return s1.toString().compareTo(s2.toString());    }     public static void main(String[] args)    {        Set<StringBuffer> str = new TreeSet<>(new Test());        str.add(new StringBuffer("Sohan"));        str.add(new StringBuffer("Raja"));        str.add(new StringBuffer("Harish"));        str.add(new StringBuffer("Ram"));        System.out.println(str);    }}
Output: 
[Harish, Raja, Ram, Sohan]

This article is contributed by Sajid Ali Khan and improvisation by Soumyaranjan Panda. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
soumyaranjanpanda177
Java-String-Programs
java-StringBuffer
Java-Strings
Java
Java-Strings
Java
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.
Comments
Old Comments
Different ways of Reading a text file in Java
Constructors in Java
Stream In Java
Generics in Java
Exceptions in Java
Functional Interfaces in Java
Comparator Interface in Java with Examples
HashMap get() Method in Java
Strings in Java
StringBuilder Class in Java with Examples