import java.util.*;
public class TreeSetTest4 {
public static void main(String[] args) {
System.out.println("Please input a string:");
Scanner in = new Scanner(System.in);
String s = in.nextLine();
char[] array = s.toCharArray();
TreeSet ts = new TreeSet(new Comparator() {
public int compare(Object o1,Object o2) {
Character c1 = (Character)o1;
Character c2 = (Character)o2;
//字符本身具备compareTo比较规则,按照字母先后顺序排列
int num = c1.compareTo(c2);
//防止相等的时候去重,因为相等时返回0,所以不要让它返回0即可
return num == 0 ? 1 : num;
}
});
for(int i = 0;i<array.length;i++) {
ts.add(array[i]);
}
Iterator iter = ts.iterator();
while(iter.hasNext()) {
System.out.print(iter.next());
}
System.out.println();
}
}