remove duplicates from string , logic is not working

You can use this:

public static void main(String[] args) {
		   String input = "manishaam";

		    String output = "";
		    for (int index = 0; index < input.length(); index++) {
		        if (input.charAt(index % input.length()) != input
		                .charAt((index + 1) % input.length())) {

		            output += input.charAt(index);

		        }
		    }
		    System.out.println(output);
	}

There is a problem in which you are traversing the second for loop

Or Y

public static void main(String[] args) {

		String input = "manishaam";

		String result = "";
		for (int i = 0; i < input.length(); i++) {
			if (!result.contains(String.valueOf(input.charAt(i)))) {
				result += String.valueOf(input.charAt(i));
			}
		}
		
		System.out.println("Output is " + result);
	}

ou can use this as well:

Or simply use LinkedHashSet. That will remove duplicates like this:

public static void main(String[] args) {

		String string = "manishaam";
		
		char[] chars = string.toCharArray();
		Set<Character> charSet = new LinkedHashSet<Character>();
		for (char c : chars) {
		    charSet.add(c);
		}

		StringBuilder sb = new StringBuilder();
		for (Character character : charSet) {
		    sb.append(character);
		}
		System.out.println(sb.toString());
	}