how to print the duplicate letters in a string?

Below Code may help you for this.

package general;

public class PrintDuplicateLetterInString {

public static void main(String[] args) {

//String ip="navneet";
String ip="aaaa";
char [] input = ip.toCharArray();
System.out.println("Duplicate Characters are as follows:");
for(int i=0;i<ip.length();i++)
{
for(int j=i+1;j<ip.length();j++)
{
if(input[i]==input[j])
{
System.out.println(input[j]);
break;
}
}
}


}

}