Flash cards
Review the key moves
1/4
Core idea
What is the main idea behind Java How To - Character Frequency in a String?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
1Quick choice
Which statement best captures the main point of this lesson?
2Fill blank
Complete the missing token from the example code.
___ java.util.HashMap;3Order
Put the learning moves in the order that makes the concept easiest to apply.
Explanation: We loop through each character in the string and use a HashMap to keep track of counts.
Use a HashMap to count how many times each character appears:
How To Count Character Frequency in a String
How To Count Character Frequency in a String
Use a HashMap to count how many times each character appears:
Example
import java.util.HashMap;
public class Main {
public static void main(String[] args) {
String text = "banana";
HashMap<Character, Integer> freq = new HashMap<>();
for (char c : text.toCharArray()) {
freq.put(c, freq.getOrDefault(c, 0) + 1);
}
System.out.println(freq);
// Output: {a=3, b=1, n=2}
}
}Explanation: We loop through each character in the string and use a HashMap to keep track of counts. - freq.getOrDefault(c, 0) means "get the current count of this character, or 0 if it hasn't been seen yet." - We then add 1 and put the new value back in the map. For the string "banana" , the result is {a=3, b=1, n=2} .