public class Main { public static void main(String[] args) { char[] str = {'d','a','b','c','d'}; for(char a:str){ System.out.print(a); } System.out.println(""); int[] number = new int[26]; for(char a:str){ number[a-'a']++ ; } for(int i=0;i<str.length;i++){ if(number[str[i]-'a']>1){ number[str[i]-'a']-- ; str[i]='0'; } } for(char a:str){ if(a!='0') System.out.print(a); } } }