Below program illustrates how to print duplicate characters in given String using Java:

public class DuplicateStringCharacters {
 
	public static void main(String[] args) {
		String str = "SACHINTENDULKAR";
		printDuplicateCharacters(str);
 
	}
 
	private static void printDuplicateCharacters(String str) {
		Set<Character> set = new HashSet<>();
		Set<Character> duplicates = new HashSet<>();
		char[] chars = str.toCharArray();
		for (char ch : chars) {
			boolean isAdded = set.add(ch);
			if (!isAdded) {
				duplicates.add(ch);
			}
		}
 
		for (char ch : duplicates) {
			System.out.print(ch + " ");
		}
	}
}