How to count number of occurrences of pattern within a string?

Counting occurrences of numbers in an array?

• I am trying to write a program which randomly picks 100 integers from 0 - 99, displays the numbers, and counts the occurrences of of each number and lists them. I have successfully written the code to generate the random array of 100 integers, but my counts are way off, and at the end of my count line, it keeps printing an array reference number, not the value. The code is listed below public class CountNumbers { /** * @param args */ public static void main(String[] args) { // Declare and create an array int[] numbers = createArray(); //Display the array System.out.println("The random integers between 0 and 9 are:"); displayArray(numbers); //count the occurrences of each number int[] counts = countOccur(numbers); //Display Counts System.out.println(); System.out.println("The occurrences of each number are:"); displayCounts(counts); System.out.println(counts); } // create an array of numbers public static int[] createArray() { // Declare an array of characters and create it int[] numbers = new int[100]; //Create numbers randomly and assign //them to the array for (int i = 0; i < numbers.length; i++) numbers[i] = (int)(Math.random() * 10); //return the array return numbers; } // Display the array of characters public static void displayArray(int[] numbers) { //Display the characters in the array 20 on each line for (int i = 0; i < numbers.length; i++) if ((i + 1) % 20 == 0) System.out.println(numbers[i]); else System.out.print(numbers[i] + " "); } // count the occurrences of each number public static int[] countOccur(int[] numbers) { //Declare an array of 10 integers int [] counts = new int[10]; //for each specific number in the array, count it for (int i = 0; i < counts.length; i++) counts[numbers[i]]++; return counts; } public static void displayCounts(int[] counts) { for(int i = 0; i < 10; i++) { if ((i + 1) % 10 == 0) System.out.println(i + ": " + counts[i]+ " | "); else System.out.print(i + ": " + counts[i] + " | " + " "); } } }

• Answer:

  This looks like homework so I'm not just going to hand you the answer, but here's a hint. The reason why your counts are way off is this:   for (int i = 0; i < counts.length; i++)       counts[numbers[i]]++; How many times does that loop repeat? Is that enough for it to examine every item in the 'numbers' array? The reason why the array's identity is printed at the very end is this line:   System.out.println(counts); The only reason I can think of for why that line even exists is that it might be a leftover from your first pass at writing an outline of the program. The fix should be obvious.