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JAVA: check a string if there is a special character in it
I am a novice programmer and am looking for help determining if a character is a special character. My program asks the user to input the name of a file, and the program reads the text in the file and determines how many blanks spaces, digits, letters, and special characters are in the text. I have the code completed to determine the blanks, digits, and letters, however am unsure of how to check if a character is a special character. Any help you can offer is appreciated and if something was not clear enough I can try to elaborate. My code so far is:
import java.util.Scanner;
import java.io.*;
public class TextFile{
public static void main(String[] args){
Scanner input = new Scanner (System.in);
String fileName;
boolean goodName = false;
int blankCount = 0;
int letterCount = 0;
int digitCount = 0;
int specialcharCount = 0;
String currentLine;
char c;
Scanner lineFile= null;
FileReader infile;
System.out.println("Please enter the name of the file: ");
fileName = input.nextLine();
while (!goodName) {
try{
infile = new FileReader(fileName);
lineFile = new Scanner(infile);
goodName= true;
}
catch(IOException e) {
System.out.println("Invalid file name, please enter correct file name: ");
fileName=input.nextLine();
}
}
while (lineFile.hasNextLine()){
currentLine = lineFile.nextLine();
for(int j=0; j<currentLine.length();j++){
c=currentLine.charAt(j);
if(c== ' ') blankCount++;
if(Character.isDigit(c)) digitCount++;
if(Character.isLetter(c)) letterCount++;
if() specialcharCount++;
}
}
}
}
I need something to put in the if statement at the end to increment specialcharCount.
This question is related to
java
special-characters
You can use regular expressions.
String input = ...
if (input.matches("[^a-zA-Z0-9 ]"))
If your definition of a 'special character' is simply anything that doesn't apply to your other filters that you already have, then you can simply add an else
. Also note that you have to use else if
in this case:
if(c == ' ') {
blankCount++;
} else if (Character.isDigit(c)) {
digitCount++;
} else if (Character.isLetter(c)) {
letterCount++;
} else {
specialcharCount++;
}
Take a look at class java.lang.Character
static member methods (isDigit, isLetter, isLowerCase, ...)
Example:
String str = "Hello World 123 !!";
int specials = 0, digits = 0, letters = 0, spaces = 0;
for (int i = 0; i < str.length(); ++i) {
char ch = str.charAt(i);
if (!Character.isDigit(ch) && !Character.isLetter(ch) && !Character.isSpace(ch)) {
++specials;
} else if (Character.isDigit(ch)) {
++digits;
} else if (Character.isSpace(ch)) {
++spaces;
} else {
++letters;
}
}
This method checks if a String contains a special character (based on your definition).
/**
* Returns true if s contains any character other than
* letters, numbers, or spaces. Returns false otherwise.
*/
public boolean containsSpecialCharacter(String s) {
return (s == null) ? false : s.matches("[^A-Za-z0-9 ]");
}
You can use the same logic to count special characters in a string like this:
/**
* Counts the number of special characters in s.
*/
public int getSpecialCharacterCount(String s) {
if (s == null || s.trim().isEmpty()) {
return 0;
}
int theCount = 0;
for (int i = 0; i < s.length(); i++) {
if (s.substring(i, 1).matches("[^A-Za-z0-9 ]")) {
theCount++;
}
}
return theCount;
}
Another approach is to put all the special chars in a String and use String.contains:
/**
* Counts the number of special characters in s.
*/
public int getSpecialCharacterCount(String s) {
if (s == null || s.trim().isEmpty()) {
return 0;
}
int theCount = 0;
String specialChars = "/*!@#$%^&*()\"{}_[]|\\?/<>,.";
for (int i = 0; i < s.length(); i++) {
if (specialChars.contains(s.substring(i, 1))) {
theCount++;
}
}
return theCount;
}
NOTE: You must escape the backslash and "
character with a backslashes.
The above are examples of how to approach this problem in general.
For your exact problem as stated in the question, the answer by @LanguagesNamedAfterCoffee is the most efficient approach.
What I would do:
char c;
int cint;
for(int n = 0; n < str.length(); n ++;)
{
c = str.charAt(n);
cint = (int)c;
if(cint <48 || (cint > 57 && cint < 65) || (cint > 90 && cint < 97) || cint > 122)
{
specialCharacterCount++
}
}
That is a simple way to do things, without having to import any special classes. Stick it in a method, or put it straight into the main code.
ASCII chart: http://www.gophoto.it/view.php?i=http://i.msdn.microsoft.com/dynimg/IC102418.gif#.UHsqxFEmG08
Source: Stackoverflow.com