Dear readers, today we create a program which is find duplicate characters in a String and would display the count of them.
Java Program to find duplicate Characters in a String using HashMap
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
public class Details {
public void countDupChars(String str){
//Create a HashMap
Map<Character, Integer> map = new HashMap<Character, Integer>();
//Convert the String to char array
char[] chars = str.toCharArray();
/* logic: char are inserted as keys and their count
* as values. If map contains the char already then
* increase the value by 1
*/
for(Character ch:chars){
if(map.containsKey(ch)){
map.put(ch, map.get(ch)+1);
} else {
map.put(ch, 1);
}
}
//Obtaining set of keys
Set<Character> keys = map.keySet();
/* Display count of chars if it is
* greater than 1. All duplicate chars would be
* having value greater than 1.
*/
for(Character ch:keys){
if(map.get(ch) > 1){
System.out.println("Char "+ch+" "+map.get(ch));
}
}
}
public static void main(String a[]){
Details obj = new Details();
System.out.println("String: fastread.in");
System.out.println("-------------------------");
obj.countDupChars("fastread.in");
System.out.println("\nString: Manishadubey");
System.out.println("-------------------------");
obj.countDupChars("Manishadubey");
System.out.println("\nString: #@$@!#$%!!%@");
System.out.println("-------------------------");
obj.countDupChars("#@$@!#$%!!%@");
}
}
Output:
String: fastread.in ------------------------- Char e 1 Char t 1 Char a 2 Char s 1 String: Manishadubey ------------------------- Char a 2 Char s 1 Char h 1 Char e 1 String: #@$@!#$%!!%@ ------------------------- Char # 2 Char ! 3 Char @ 3 Char $ 2 Char % 2