In this article, we will count and print number of repeated character occurrences in a String i.e.;
1. Counting & printing in a String :
- Number of repeated character occurrences
- Along with its count
Note:- Same example is implemented using Java 1.8 version and Stream, check Java 8 – Count and print number of repeated character occurrences in a String
1.1 Steps for counting repeated character occurrences :
- Create empty HashMap of type Character & Integer
- Convert String into character[] array using toCharArray() method of String class
- Iterate through character[] array
- Leave blank spaces in between 2 words in a String sentence
- Check whether particular character present in the HashMap using containsKey(k) method of Map interface
- If it contains, then increase the count value by 1 using put(K, V) method of Map interface
- Otherwise insert using put() method of Map with count value as 1
- Get keySet() for iterating through Map
- Finally, print character[] array using for-each loop
- Code sorting logic for printing count value in descending order using Comparator interface
- Again print after sorting
ReadCountPrintRepeatedCharacterOccurencesInString.java
package in.bench.resources.count.print.occurences;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
public class ReadCountPrintRepeatedCharacterOccurencesInString {
public static void main(String[] args) {
// sample test string
String testStr = "Spring and Hibernate";
// invoke to count & print for supplied file
countAndPrintRepeatedCharacterOccurences(testStr);
}
/**
* this method is used
* to count number repeated word occurrences
* @param fileName
*/
public static void countAndPrintRepeatedCharacterOccurences(
String strContent) {
// Step 1: create Map of Character-Integer
Map<Character, Integer> mapOfRepeatedChar =
new HashMap<Character, Integer>();
// Step 2: convert String into character-array
// using toCharArray() method
char[] chArray = strContent.toCharArray();
// Step 3: iterate through char[] array
for(char ch : chArray) {
// Step 4: leave spaces
if(ch != ' '){
// Step 5: check
// whether Map contains particular character
if(mapOfRepeatedChar.containsKey(ch)){
// Step 6: If contains,
// increase count value by 1
mapOfRepeatedChar.put(ch,
mapOfRepeatedChar.get(ch) + 1);
}
else {
// Step 7: otherwise, make a new entry
mapOfRepeatedChar.put(ch, 1);
}
}
}
System.out.println("Before sorting : \n");
System.out.println("Char" + "\t" + "Count");
System.out.println("====" + "\t" + "=====");
// Step 8: get keySet() for iteration
Set<Character> character = mapOfRepeatedChar.keySet();
// Step 9: print word along with its count
for(Character ch : character) {
System.out.println(ch
+ "\t" + mapOfRepeatedChar.get(ch));
}
// Step 10: Sorting logic by invoking sortByCountValue()
Map<Character, Integer> wordLHMap = sortByCountValue(
mapOfRepeatedChar);
System.out.println("\n\nAfter sorting"
+ " in descending order of count : \n");
System.out.println("Char" + "\t" + "Count");
System.out.println("====" + "\t" + "=====");
// Step 11: Again print after sorting
for(Map.Entry<Character, Integer> entry :
wordLHMap.entrySet()){
System.out.println(entry.getKey()
+ "\t" + entry.getValue());
}
}
/**
* this method sort acc. to count value
* @param mapOfRepeatedWord
* @return
*/
public static Map<Character, Integer> sortByCountValue(
Map<Character, Integer> mapOfRepeatedWord) {
// get entrySet from HashMap object
Set<Map.Entry<Character, Integer>> setOfWordEntries =
mapOfRepeatedWord.entrySet();
// convert HashMap to List of Map entries
List<Map.Entry<Character, Integer>> listOfwordEntry =
new ArrayList<Map.Entry<Character, Integer>>(
setOfWordEntries);
// sort list of entries using Collections.sort(ls, cmptr);
Collections.sort(listOfwordEntry,
new Comparator<Map.Entry<Character, Integer>>() {
@Override
public int compare(Entry<Character, Integer> es1,
Entry<Character, Integer> es2) {
return es2.getValue().compareTo(es1.getValue());
}
});
// store into LinkedHashMap for maintaining insertion
Map<Character, Integer> wordLHMap =
new LinkedHashMap<Character, Integer>();
// iterating list and storing in LinkedHahsMap
for(Map.Entry<Character, Integer> map : listOfwordEntry){
wordLHMap.put(map.getKey(), map.getValue());
}
return wordLHMap;
}
}
Output:
Before sorting :
Char Count
==== =====
p 1
a 2
r 2
b 1
S 1
d 1
t 1
e 2
g 1
H 1
i 2
n 3
After sorting in descending order of count :
Char Count
==== =====
n 3
a 2
r 2
e 2
i 2
p 1
b 1
S 1
d 1
t 1
g 1
H 1
Note: Stop at Step 9, if there is no business requirements for sorting either way (ascending or descending)
2. Reading from file in Java 1.7 version :
- In the above example, we counted repeated words from String content
- Similarly, we can read file from local drive location and count number of repeated words
- While doing so, we need to provide catch block with FileNotFoundException and IOException for exception raised, as we are dealing with files
- We will use try-with-resources statement introduced in Java 1.7 version, as it handles automatic resource management (ARM) implicitly i.e.; auto-closing of opened resources without explicit closing inside finally block after necessary null-safety checks
- Thus, it improves readability of the code by reducing number of lines of code
Sample text file:
ReadPrintCharFromFileInJava7.java
package in.bench.resources.count.print.occurences;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
public class ReadPrintCharFromFileInJava7 {
public static void main(String[] args) {
// invoke to count & print for supplied file
countAndPrintRepeatedCharacterOccurences("D://WORKSPACE/"
+ "TEST_WORKSPACE/Java_8_Project/BRN2.txt");
}
/**
* this method is used
* to count number repeated word occurrences
* @param fileName
*/
public static void countAndPrintRepeatedCharacterOccurences(
String fileName) {
// local variables
String line = "";
// Step 1: create Map of Character-Integer
Map<Character, Integer> mapOfRepeatedChar =
new HashMap<Character, Integer>();
// Step A: Read file using try-with-resources statement
try(BufferedReader bufferedReader =
new BufferedReader(new FileReader(fileName))) {
// Step B: Read line from file
while ((line = bufferedReader.readLine()) != null) {
// Step 2: convert String into character-array
// using toCharArray() method
char[] chArray = line.toCharArray();
// Step 3: iterate through char[] array
for(char ch : chArray) {
// Step 4: leave spaces
if(ch != ' '){
// Step 4.1: convert all,
// char into upper case, before comparison
char upperChar= Character.toUpperCase(ch);
// Step 5: check
// whether Map contains same character
if(mapOfRepeatedChar
.containsKey(upperChar)) {
// Step 6: If contains,
// increase count value by 1
mapOfRepeatedChar.put(upperChar,
mapOfRepeatedChar.get(
upperChar) + 1);
}
else {
// Step 7: otherwise, make a new entry
mapOfRepeatedChar.put(upperChar, 1);
}
}
}
}
System.out.println("Before sorting : \n");
System.out.println("Char" + "\t" + "Count");
System.out.println("====" + "\t" + "=====");
// Step 8: get keySet() for iteration
Set<Character> character = mapOfRepeatedChar.keySet();
// Step 9: print word along with its count
for(Character ch : character) {
System.out.println(ch
+ "\t" + mapOfRepeatedChar.get(ch));
}
// Step 10: Sorting
// provide logic by invoking sortByCountValue();
Map<Character, Integer> wordLHMap = sortByCountValue(
mapOfRepeatedChar);
System.out.println("\n\nAfter sorting"
+ " in descending order of count : \n");
System.out.println("Char" + "\t" + "Count");
System.out.println("====" + "\t" + "=====");
// Step 11: Again print after sorting
for(Map.Entry<Character, Integer> entry :
wordLHMap.entrySet()){
System.out.println(entry.getKey()
+ "\t" + entry.getValue());
}
}
catch (FileNotFoundException fnfex) {
fnfex.printStackTrace();
}
catch (IOException ioex) {
ioex.printStackTrace();
}
}
/**
* this method sort acc. to count value
* @param mapOfRepeatedWord
* @return
*/
public static Map<Character, Integer> sortByCountValue(
Map<Character, Integer> mapOfRepeatedWord) {
// get entrySet from HashMap object
Set<Map.Entry<Character, Integer>> setOfWordEntries =
mapOfRepeatedWord.entrySet();
// convert HashMap to List of Map entries
List<Map.Entry<Character, Integer>> listOfwordEntry =
new ArrayList<Map.Entry<Character, Integer>>(
setOfWordEntries);
// sort list of entries using Collections.sort(ls, cmptr);
Collections.sort(listOfwordEntry,
new Comparator<Map.Entry<Character, Integer>>() {
@Override
public int compare(Entry<Character, Integer> es1,
Entry<Character, Integer> es2) {
return es2.getValue().compareTo(es1.getValue());
}
});
// store into LinkedHashMap for maintaining insertion
Map<Character, Integer> wordLHMap =
new LinkedHashMap<Character, Integer>();
// iterating list and storing in LinkedHahsMap
for(Map.Entry<Character, Integer> map : listOfwordEntry) {
wordLHMap.put(map.getKey(), map.getValue());
}
return wordLHMap;
}
}
Output:
Before sorting :
Char Count
==== =====
A 6
B 4
C 3
E 2
H 3
I 2
K 4
L 4
M 2
N 5
P 1
S 5
T 2
Y 1
After sorting in descending order of count :
Char Count
==== =====
A 6
N 5
S 5
B 4
K 4
L 4
C 3
H 3
E 2
I 2
M 2
T 2
P 1
Y 1
Note: Stop at Step 9, if there is no business requirements for sorting either way (ascending or descending)
Related Articles:
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- Java 8 – Count and print number of repeated word occurrences in a text file
- Java 8 – Count and print number of repeated character occurrences in a String
- Java – Count and print number of words and lines in a text file
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