Java中的重复输出

我是新来的，还在学习.今天我学会了在字符串中查找重复项.从https://www.javatpoint.com/program-to-find-the-duplicate-characters-in-a-string岁开始，我试着从网上学习完整的代码.

当string="Great responsibility"时，输出为:

 Duplicate characters in a given string: 
r
e
t
s
i

因为它有重复的字符

当字符串"很棒"时，输出是

 Duplicate characters in a given string: 

输出是空白的，因为没有重复的字符，所以我给出了一个描述"无重复"来定义无字符重复，输出如下

Duplicate characters in a given string: 
no duplicates
no duplicates
no duplicates
no duplicates
no duplicates

这会返回太多描述.

我的密码

public class DuplicateCharacters {  
    public static void main(String[] args) {  
        String string1 = "Great";  
        int count;  
          
        //Converts given string into character array  
        char string[] = string1.toCharArray();  
          
        System.out.println("Duplicate characters in a given string: ");  
        //Counts each character present in the string  
        for(int i = 0; i <string.length; i++) {  
            count = 1;  
            for(int j = i+1; j <string.length; j++) {  
                if(string[i] == string[j] && string[i] != ' ') {  
                    count++;  
                    //Set string[j] to 0 to avoid printing visited character  
                    string[j] = '0';  
                }  
            }  
            //A character is considered as duplicate if count is greater than 1  
            if(count > 1 && string[i] != '0')  
                System.out.println(string[i]);  
            else 
             System.out.println("no duplicates"); 
        }  
    }  
} 

如何只打印一个描述而不重复？我try 返回0；但它不起作用.

预期yields

Duplicate characters in a given string: 
no duplicates