Java program to remove duplicate characters from a string

In this article we will learn to implement a Java program to remove duplicate characters from a string. A java program is provided below that accepts a string from the user, ignores any duplicate characters and prints each character only once in ascending order.

We use TreeSet class from collections framework for printing the characters in ascending order.

The program is as follows:

import java.util.*;
public class Sample 
{

	public static void main(String[] args) 
	{
		TreeSet<Character> list = new TreeSet<Character>();
		Scanner input = new Scanner(System.in);
		String s = input.next();
		for(char ch : s.toCharArray())
			list.add(ch);
		for(char ch : list)
			System.out.println(ch);
	}
}

Input and output for the above program is as follows:

Input:
asaabebys

Output:
a
b
e
s
y

If you want to display in insertion order, you can use LinkedHashSet.

Suryateja Pericherla

Suryateja Pericherla, at present is a Research Scholar (full-time Ph.D.) in the Dept. of Computer Science & Systems Engineering at Andhra University, Visakhapatnam. Previously worked as an Associate Professor in the Dept. of CSE at Vishnu Institute of Technology, India.

He has 11+ years of teaching experience and is an individual researcher whose research interests are Cloud Computing, Internet of Things, Computer Security, Network Security and Blockchain.

He is a member of professional societies like IEEE, ACM, CSI and ISCA. He published several research papers which are indexed by SCIE, WoS, Scopus, Springer and others.