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Sep 3rd, 2006

Character Frequency

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I am trying to write a code to count the frequency of characters in a String;

For example if I have String str = new String("This is a test");

I want to count the number of occurrence of each character in the string.(assuming the code is case insensitive)

This is what I have at present ...

Java Syntax (Toggle Plain Text)
 
//
 
 
public static void main(String[] args) 
{
// TODO Auto-generated method stub
 
String temp = new String("This is a test message");
//int[] alphabets = new int [26];
int [] temp1 = new int[100];
char [] s = temp.toUpperCase().toCharArray();
 
 
for(int i=0;i<s.length;i++)
{
temp1[(s-'A')]++;
}
 
      for(int i =0;i<temp1.length;i++)
      {
         System.out.println(temp1);
       }
 
}
 
}
 
}
//


public static void main(String[] args) 
{
// TODO Auto-generated method stub

String temp = new String("This is a test message");
//int[] alphabets = new int [26];
int [] temp1 = new int[100];
char [] s = temp.toUpperCase().toCharArray();


for(int i=0;i<s.length;i++)
{
temp1[(s-'A')]++;
}

      for(int i =0;i<temp1.length;i++)
      {
         System.out.println(temp1);
       }

}

}

}

I need help on how to complete this implementation.

Thanks in advance for your help.

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crestaldin

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since Mar 2005

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Sep 3rd, 2006

Re: Character Frequency

Yeah, we're not suppose to do your homework for you bud.

Do you have to use arrays? It might be best to use a HashMap here. Using a HashMap will allow you to count only the characters that you have and nothing else. However, you will have to make a lot of objects to make it work.

You also might want to look at the String methods .toUpperCase() and .toLowerCase().

hooknc

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since Aug 2005

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Sep 3rd, 2006

Re: Character Frequency

Click to Expand / Collapse Quote originally posted by hooknc ...

Yeah, we're not suppose to do your homework for you bud.

Do you have to use arrays? It might be best to use a HashMap here. Using a HashMap will allow you to count only the characters that you have and nothing else. However, you will have to make a lot of objects to make it work.

You also might want to look at the String methods .toUpperCase() and .toLowerCase().

Thank you for the suggestion but ... that's actually not my homework. I just went online (http://cs.furman.edu/ccscse2002/prog...gcont_1995.pdf ) to get a website with Java problems and I'm working on them to improve on my skills.

crestaldin

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Sep 5th, 2006

Re: Character Frequency

Java Syntax (Toggle Plain Text)
HashMap freqMap = new HashMap();
 
//FOR loop through chars goes here
if (freqMap.containsKey(character))
    freqMap.put(character, freqMap.get(character)+1);
else
    freqMap.put(character, 1);
HashMap freqMap = new HashMap();
 
//FOR loop through chars goes here
if (freqMap.containsKey(character))
    freqMap.put(character, freqMap.get(character)+1);
else
    freqMap.put(character, 1);

Don't expect that code to work with a copy n paste job, you'll still need to do some casting and boxing.

You can even condense that 4-line IF statement into a single line using the alternative IF structure. Once you've solved this problem successfully, I'll show you how if interested.

Phaelax

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Practically a Posting Shark

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856 posts
since Mar 2004

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Jun 2nd, 2010

Re: Character Frequency

Try this..

public void getFrequencyInString(){
String str = "apple";
HashMap hm = new HashMap();
for(int i = 0; i<str.length(); i++){
char c = str.charAt(i);
if(hm.get(c)!= null){
hm.put(c, (Integer)(hm.get(c))+1);
}else{
hm.put(c, 1);
}
}
System.out.println(hm.entrySet());
}
Output: [e=1, p=2, a=1, l=1]

Vijay1214

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