Java Program to find Duplicate Character In String ?

Below example show how to count repeated characters from String.

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

public class DuplicateCharacterFromString {

public static void method(String str){
Map<Character, Integer> map = new HashMap<>();
for(int i=0;i<str.length();i++){
if(map.containsKey(str.charAt(i))){
map.put(str.charAt(i), map.get(str.charAt(i))+1);
}
else{
map.put(str.charAt(i), 1);
}
}
Set<Character> set = map.keySet();
for(Character c : set){
if(map.get(c) > 1){
System.out.println(c+":"+map.get(c));
}
}
}
public static void main(String[] args) {
DuplicateCharacterFromString.method("abca");
}


}
Program Output :-

a:2