Array Histogram

Hello, I'm having trouble coding a program which reads in strings (search terms) from a file, orders them, and then creates a histogram showing the occurrence of each string length.

For example, if the search terms were: frog, cat, dog; the program would print the following output:

Search Terms
-------------
frog
cat
dog

Term Length ... Count
------------ ... ------
3 .................... 2
4 .................... 1

I have the program reading in terms and sorting them, but I can't get the histogram to display the number of occurrences for each term.

I get output like this:
3 .......... 1
3 .......... 1
4 .......... 1

I know it's a logic error, but what should I be doing?

Code Java:

---

package nicepackage;
 
import java.io.*;
import java.util.Scanner;
 
public class Search {
 
	/**
	 * @param args
	 */
	public static void main(String[] args) throws Exception {
		System.out.println("\nSearch Terms");
		System.out.print("------------");
 
		FileReader fr1 = new FileReader("C:\\users\\T\\inSearchterms.txt");
		Scanner inFr1 = new Scanner (fr1);
 
		int n = inFr1.nextInt()+1;
		String[] a = new String[n];
		for (int i=0; i<n; i++)
		{
			a[i]= inFr1.nextLine();
			//System.out.println(a[i]);
		}
		selectionSort(a);
		System.out.println("\nTerm Length	Count");
		System.out.println("-----------	-----");
 
		int[] histogram = new int[n];
		int[] ct = new int[n];
 
		for (int b=1; b <= a.length-1; b++)
		{
			for (int d = 30; d >= 0; d--)
			{
				if (d == a[b].length())
				{
					histogram[b] = a[b].length();
					ct[b]++;
				}
			}
			System.out.println(histogram[b] + "		" + ct[b]);
		}
	}
 
	public static void selectionSort (String [] a)
	{
		for (int i=a.length-1; i >= 1; i--)
		{
			String currentMax = a[0];
			int currentMaxIndex = 0;
			for (int j=1; j <= i; j++)
			{
				if (currentMax.compareToIgnoreCase(a[j])<0)
				{
					currentMax = a[j];
					currentMaxIndex = j;
				}
			}
			if (currentMaxIndex != i)
			{
				a[currentMaxIndex] = a[i];
				a[i] = currentMax;
			}
			//System.out.println("/"+a[i]);
		}
 
	}
}

---

What am I doing wrong? Any help is greatly appreciated, thanks!

Do you know how to use a Map? It would be useful: key=length of String, value=count

Otherwise use an array. What is the max String length? Have an array with a slot for each length and increment the slots as per String length.

Unfortunately, I don't know how to use a Map.

I need the program to determine the max String length, can I do that using the process you described? If I'm understanding correctly, I think that's what I'm trying to do. I set up two int arrays, one called histogram and one called ct, each with as many slots as there are terms in the file (or at least that's what I intended to do).

Read all the strings and remember the length of the longest one, create the array then read them again and count the lengths.

I know that the longest String in the file I'm using is 26 characters, but I can't just create the array specific to the Strings in this file because I need it to work with any file.

One way would be to make two passes. The first to find the longest, the second to count.
Another way would be to use parallel arrays, have one array contain the length, and the other the count.


Using the new collection classes would make this easier.

Thanks for your help so far.

I think I'm trying to use parallel arrays. Am I initializing them correctly in my code? I believe that's where I'm getting errors.

Quote:

---

java.lang.ArrayIndexOutOfBoundsException: 16

---

The index is past the end of the array. Remember array indexes go from 0 to the length-1

Can somebody take another look at this, please? I'm losing my mind trying to figure this out.

Please post the program's output and explain what is wrong with it and show what it should be.