Java program to print all unique words present in the string. The task is to print all words occurring only once in the string.
Illustration:
Input : Welcome to Geeks for Geeks.
Output : Welcome
to
for
Input : Java is great.Python is also great.
Output : Java
Python
also
Methods:
This can be done in the following ways:
- Using nested loops
- Using Map
- Using frequency() method of Collections
Naive approach: Using nested loops
The idea to count the occurrence of the string in the string and print if count equals one
- Extract words from string using split() method and store them in an array.
- Iterate over the word array using for loop.
- Use another loop to find the occurrence of the current word the array.
- If the second occurrence is found increment count and set the word to “”
- If the count of the current word is equal to one print it
Example:
Java
// Java Program to Print all unique words// Using nested loops// Main classpublic class GFG { // Method 1 // To print the unique words static void printUniqueWords(String str) { // Maintaining a count variable int count; // Extract words from string // using split() method String[] words = str.split("\\W"); // Iterating over the words array for (int i = 0; i < words.length; i++) { // Setting count of current word to one count = 1; for (int j = i + 1; j < words.length; j++) { if (words[i].equalsIgnoreCase(words[j])) { // If word found later in array // increment the count variable count++; words[j] = ""; } } // If count of current word is one print it if (count == 1 && words[i] != "") // Print statement System.out.println(words[i]); } } // Method 2 // Main driver method public static void main(String[] args) { // Custom input string String str = "Welcome to geeks for geeks"; // Calling the method 1 to print all unique words // in above string passed as argument printUniqueWords(str); }} |
Output
Welcome to for
Note: Time complexity is of order n^2 where space complexity is of order n
Method 2: Using Map
Approach: The idea is to use Map to keep track of words already occurred. But first, we have to extract all words from a String, as a string may contain many sentences with punctuation marks.
- Create an empty Map.
- Extract words from string using split() method and store them in an array.
- Iterate over the word array.
- Check if the word is already present in the Map or not.
- If a word is present in the map, increment its value by one.
- Else store the word as the key inside the map with value one.
- Iterate over the map and print words whose value is equal to one.
Example:
Java
// Java Program to Print all Unique Words// Using Map// Importing utility classes from java.util packageimport java.util.HashMap;import java.util.LinkedHashMap;import java.util.Map;// Main classpublic class GFG { // Method 1 // To print all unique words in the string static void printUniqueWords(String str) { // Create a new Map by creating object of HashMap // class HashMap<String, Integer> map = new LinkedHashMap<String, Integer>(); // Extract words from string // using split() method String[] words = str.split("\\W"); // Iterating over the words array // using for each loop for (String word : words) { // If the word is present in array then // if (map.containsKey(word)) { // Increment its value by one // using map.get() method map.put(word, map.get(word) + 1); } // Else store the word inside map // with value one else map.put(word, 1); } // Iterate over the map using for each loop for (Map.Entry<String, Integer> entry : map.entrySet()) { // If value of words equals unity if (entry.getValue() == 1) // Print all those words System.out.println(entry.getKey()); } } // Method 2 // Main driver method public static void main(String[] args) { // Custom input string String str = "Welcome to geeks for geeks"; // Calling the Method1 to // print all unique words in above string printUniqueWords(str); }} |
Output
Welcome to for
Note: Time complexity is of the order of n where space complexity is of order n. Hence, it is the optimal approach.
Method 3 : Using Collections.frequency() . If the occurrence of word in string is 1 , then the word is unique.
Java
// Java Program to Print all unique words// Main classimport java.util.*;public class Main{ public static void main(String[] args) { String str = "Welcome to geeks for geeks"; String[] words = str.split("\\W"); List<String> al = new ArrayList<>(Arrays.asList(words)); for(String x:al) { if(Collections.frequency(al,x)==1){ System.out.println(x); } } }} |
Output
Welcome to for
