How do you find duplicates in a string in Java?

How do you count duplicates in a string in Java?


  1. public class DuplicateCharacters {
  2. public static void main(String[] args) {
  3. String string1 = “Great responsibility”;
  4. int count;
  5. //Converts given string into character array.
  6. char string[] = string1.toCharArray();
  7. System.out.println(“Duplicate characters in a given string: “);

How do you find duplicate characters in a string in Java without using collections?


  1. Create a HashMap and character of String will be inserted as key and its count as value.
  2. If Hashamap already contains char,increase its count by 1, else put char in HashMap.
  3. If value of Char is more than 1, that means it is duplicate character in that String.

How do you find repetitive characters in a string?

An efficient solution is to use Hashing to solve this in O(N) time on average.

  1. Create an empty hash.
  2. Scan each character of input string and insert values to each keys in the hash.
  3. When any character appears more than once, hash key value is increment by 1, and return the character.
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How do I find duplicates in a string list?

Get the stream of elements in which the duplicates are to be found. For each element in the stream, count the frequency of each element, using Collections. frequency() method. Then for each element in the collection list, if the frequency of any element is more than one, then this element is a duplicate element.

How do you remove duplicate characters in a string in Java?

1) By using for loop

  1. In the first step, we have to convert the string into a character array.
  2. Calculate the size of the array.
  3. Call removeDuplicates() method by passing the character array and the length.
  4. Traverse all the characters present in the character array.
  5. Check whether the str[i] is present before or not.

How do I reverse a string?

Different ways to find the reverse of a string in the C

  1. Reverse a string using the strrev() function.
  2. Reverse a string without using the library function.
  3. Reverse a string using the recursion function.
  4. Reverse a string using for loop.
  5. Reverse a string using while loop.
  6. Reverse a string using pointers.

How do you find duplicate characters in a string map?

How do you find duplicate characters in a string?

  1. import java.util.HashMap;
  2. import java.util.Map;
  3. import java.util.Set;
  4. public class DuplicateCharFinder {
  5. public void findIt(String str) {
  6. Map<Character, Integer> baseMap = new HashMap<Character, Integer>();
  7. char[] charArray = str.toCharArray();

How do I find duplicate characters in a string in SQL Server?

SQL Server: Count Number of Occurrences of a Character or Word in a String

  1. DECLARE @tosearch VARCHAR(MAX)=’In’
  2. SELECT (DATALENGTH(@string)-DATALENGTH(REPLACE(@string,@tosearch,”)))/DATALENGTH(@tosearch)
  3. AS OccurrenceCount.

How do I find duplicate characters in a string in Kotlin?

Write a kotlin program to find out duplicate characters in a…

  1. Convert the string to all lower case first.
  2. Create HashMap with <Character,Integer>
  3. Iterate the String char by char and check its present in the hashmap or not. If not present put ..char and 1. If Present get the existing value and put…. char and value+1.
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What is anagram string?

An anagram of a string is another string that contains the same characters, only the order of characters can be different. For example, “abcd” and “dabc” are an anagram of each other.

How do you find duplicates in a list?

Check for duplicates in a list using Set & by comparing sizes

  1. Add the contents of list in a set. As set contains only unique elements, so no duplicates will be added to the set.
  2. Compare the size of set and list. If size of list & set is equal then it means no duplicates in list.

How do you find duplicates in ArrayList?


  1. Get the ArrayList with duplicate values.
  2. Create another ArrayList.
  3. Traverse through the first arraylist and store the first appearance of each element into the second arraylist using contains() method.
  4. The second ArrayList contains the elements with duplicates removed.

How does Set check for duplicates?

Each and every element in the set is unique . So that there is no duplicate element in set . Now , what happens internally when you pass duplicate elements in the add() method of the Set object , It will return false and do not add to the HashSet , as the element is already present .