Please help on Strings

[nalini peddareddy]

Hi,

I am working with Strings and i have a requirement where in i have to count the number of occurences of a character in a String.I tried doing it with indexOf() method but could not do it.Could any of u help me with this?
Its really very urgent.


Thanks, in Advance
P.N.Reddy.

[Henry Wong]

I tried doing it with indexOf() method but could not do it.

If you post what you have done so far, I am sure that there are many here that would gladly give you a hint in the right direction.

Henry

[nalini peddareddy]

Hi,

I tried starting like this. I have to count the number of times 'a' is occuring. But the indexOf and lastIndexOf() methods give the indexes.How do i write the logic to get the number of occurences? seems to be very basic.. but need help.

class CountChar
{
public static void main(String[] args)
{
countchar("banana");
}

static void countchar(String str){

int i= indexOf('a');
int j= lastIndexOf('a');
System.out.println("i is:"+i);
System.out.println("j is:"+j);

}
}


Regards,
P.N.Reddy.

[Ernest Friedman-Hill]

You want to use a "for" loop, and loop over all the characters in the String; check each one to see if it's "a", and if it is, add 1 to a counter variable. At the end, the counter has the value you want.

[Ryan McGuire]

Originally posted by Ernest Friedman-Hill:
You want to use a "for" loop, and loop over all the characters in the String; check each one to see if it's "a", and if it is, add 1 to a counter variable. At the end, the counter has the value you want.

If you want to show that you can think outside the box and you're using a recent enough version of Java, there are a couple other ways to do it:

Use String.replaceAll() and length(). What should the regexp be?

Use String.split() and {array}.length. What should THIS regexp be?

If you're really dying to use indexOf(), look at the indexOf(int, int) version and use that in, as Mr. Friedman-Hill suggested, a "for" loop. What would you use for the second int in each call? What is the terminating condition for the "for" loop?
[ July 12, 2006: Message edited by: Ryan McGuire ]

[Ken Blair]

I would go with Ernest's solution if for no other reason than it's more efficient. Thinking outside the box is great when it's a better solution, but trying to be overly clever too often results in solutions like double-checked locking.

[Henry Wong]

Another issue is that this is probably a homework question. Using a regular expression engine is probably a no-no, regardless of how "interesting" the solution may be...

Henry

[nalini peddareddy]

Thanks a lot guys, i should probably go ahead with charAt() function in a for loop. I got it.

[Nor Ha]

Does anyone know how to modify this program so that it allows a user to input a sentence into a dialog box along with a character in that sentence, and then the program counts the number of times that character appears in the sentence?

Type Sentence eter picket a pot of peppers
Type Character: e

Result
5

Since the sentence is not given, there needs to be an array, then the loop. I have not been able to find the missing piece of the loop that I need. I'll post more later if there someone who is interested in helping. Thanks

[Campbell Ritchie]

Welcome to the Ranch, Nor Ha.

You have, I think, already answered your own question. Show us all what you would do to enter a sentence from a Dialog.

If I had that assignment, I would get the String into a char[] array and traverse the array counting particular characters.

[Rob Spoor]

Originally posted by Campbell Ritchie:
Welcome to the Ranch, Nor Ha.

You have, I think, already answered your own question. Show us all what you would do to enter a sentence from a Dialog.

If I had that assignment, I would get the String into a char[] array and traverse the array counting particular characters.

Why create the extra array? Just use length() and charAt() from the string itself.

[Nor Ha]

Here is a program that does some of what I would like it to do, it does not allow the user to input the sentence into an array and then input a character to search for that value. It's fairly simple to find a value when it's a number, I can write a simple program so far. But I feel I am missing many crucial elements. I want the program to input a string into an array, then input the value to find, then total the number of times the value is found.

import java.io.*;
 
public class WordCount{
private static void linecount(String fName, BufferedReader in) throws IOException{
long numChar = 0;
long numLine=0;
long numWords = 0;
String line;
do{
line = in.readLine();
if (line != null){
numChar += line.length();
numWords += wordcount(line);
numLine++;
}
}while(line != null);
System.out.println("Enter Sentence: " + fName);
System.out.println("Enter Character: " + fName);
System.out.println("Number of characters in sentence: " + numChar);
System.out.println("Number of words: " + numWords);
System.out.println("Number of Lines: " + numLine);
}
private static void linecount(String fileName){
BufferedReader in = null;
try{
FileReader fileReader = new FileReader(fileName);
in = new BufferedReader(fileReader);
linecount(fileName,in);
}
catch(IOException e){
e.printStackTrace();
}
}
private static long wordcount(String line){
long numWords = 0;
int index = 0;
boolean prevWhiteSpace = true;
while(index < line.length()){
char c = line.charAt(index++);
boolean currWhiteSpace = Character.isWhitespace(c);
if(prevWhiteSpace && !currWhiteSpace){
numWords++;
}
prevWhiteSpace = currWhiteSpace;
}
return numWords;
}
public static void main(String[] args){
long numChar = 0;
long numLine=0;
String line;
try{
if (args.length == 0)
{
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
line = in.readLine();
numChar = line.length();
if (numChar != 0){
numLine=1;
}
System.out.println("Number of characters in sentence: " + numChar);
System.out.println("Number of words: " + wordcount(line));
System.out.println("Number of lines: " + numLine);
}else{
for(int i = 0; i < args.length; i++){
linecount(args[i]);
}
}
}
catch(IOException e){
e.printStackTrace();
}
}
}

[ October 19, 2007: Message edited by: Nor Ha ]