In this post, we will see how to find duplicate Characters in a String.
When you run above program, you will get below output:
Approach:
- Create a HashMap and character of String will be inserted as key and its count as value.
- If Hashamap already contains char,increase its count by 1, else put char in HashMap
- If value of Char is more than 1, that means it is duplicate character in that String
Java Program to find duplicate Characters in a String
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package org.arpit.java2blog; import java.util.HashMap; import java.util.Set; public class StringFindDuplicatesMain { public static void main(String[] args) { String str = "java2blog.com "; HashMap charCountMap = new HashMap(); for (int i = 0; i < str.length(); i++) { char c = str.charAt(i); if (charCountMap.containsKey(c)) { charCountMap.put(c, charCountMap.get(c) + 1); } else { charCountMap.put(c, 1); } } for (Character c : charCountMap.keySet()) { if (charCountMap.get(c) > 1) System.out.println("duplicate character : " + c + " ====== " + " count : " + charCountMap.get(c)); } } } |
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duplicate character : a ====== count : 2 duplicate character : o ====== count : 2 |
Other String Programs :
- How to reverse String in java
- How to check if two Strings are angrams
- Find length of String without using java inbuilt length method
- Find all substrings of String in java
- Find First non repeated character in a String
- Java Program to check Palindrome String
- Why String is immutable in java
- Find duplicate characters in String
How about using a Set?
private static boolean hasDupeLetter(String str) {
if(null == str || str.length() <= 1) { return false; } Set set = new HashSet ();
for(int i = 0; i < str.length(); i++) { set.add(str.charAt(i)); } return str.length() == set.size(); }