Find the amount of times a number appears in the array

public int numTimes(int numToFind, int[] array)

{

int count = 0;

for(int i : array)

{

if(i == numToFind)

{

count++;

}

}

return count;

}

CaptainMorgan08a at 2007-7-12 17:28:53 >

> I am kind of new to java, just to be sure will that

> method find the amount of times numbers in an array

The best way to be sure of anything would be to take the method, put in code, compile it and run it and see what happens.

Please note you are going to have to make an effort to complete your own homework assignment. CaptainMorgan gave you a good start but it looks from your last post that you still have some work to do.

cotton.ma at 2007-7-12 17:28:53 >

public int numTimes(int numToFind, int[] array) {

String s = Arrays.toString(array);

String[] tokens = s.split("[^" + numToFind +"]+");

return tokens.length - 1;

Since we're posting solutions. However, someone will need to check my regex as it gives one too many tokens.

floundera at 2007-7-12 17:28:53 >

> I have no idea what a map is, I am new to java

Getting started with Java

[url=http://java.sun.com/docs/books/tutorial/ ]Sun's basic Java tutorial[/url]

[url=http://java.sun.com/learning/new2java/index.html ]Sun's New To Java Center[/url]. Includes an overview of what Java is, instructions for setting up Java, an intro to programming (that includes links to the above tutorial or to parts of it), quizzes, a list of resources, and info on certification and courses.

[url=http://javaalmanac.com ]http://javaalmanac.com [/url]. A couple dozen code examples that supplement [url=http://www.amazon.com/exec/obidos/tg/detail/-/0201752808?v=glance ]The Java Developers Almanac[/url].

cotton.ma at 2007-7-21 21:49:26 >

> It has to automatically do all numbers.

Your example only includes ints. So it may include an array of double? The reason I ask, is that checking equality in doubles can be somewhat trickier than for ints.

Again, if there is low chance that you will be dealing with doubles (or floats), keep the array an array of ints.

petes1234a at 2007-7-21 21:49:26 >

I have tried and came up with this:

public class Amount{

public static void main (String [] args){

int[] abc = {6, 3, 35, 353, 55 , 6, 4, 23, 6, 8, 10};

String[] def = new String[10];

int count = 0;

for(int i = 0; abc[i] < abc.length; i++){

for(int b = 0; abc[b] < abc.length; b++){

if(abc[i] == abc[b]){

count++;

}

}

def[i] = ("The Number " + abc[i] + " appears " + count + "times");

}

int d = 0;

for(int q = 0; q < def.length; q++){

if(def[q].equals(def[d])){

def[q] = def[d];

}

d++;

}

for(int w = 0; w < def.length; w++){

System.out.println(def[w]);

}

}

}

The problem is I get a null pointer exception. I try to put it in strings and then check the strings against each other.

seithexa at 2007-7-21 21:49:26 >

yeah, thanks for pointing that out, that was a huge problem, I changed it a little

public class Amount{

public static void main (String [] args){

int[] abc = {6, 3, 35, 353, 55 , 6, 4, 23, 6, 8, 10};

String[] def = new String[10];

int count = 0;

for(int i = 0; i < abc.length; i++){

for(int b = 0; b < abc.length; b++){

if(abc[i] == abc[b]){

count++;

}

}

def[i] = ("The Number " + abc[i] + " appears " + count + "times");

}

int d = 1;

for(int q = 0; q < def.length; q++){

if(def[q].equals(def[d])){

def[q] = def[d];

}else{

def[q] = def[q];

}

d++;

}

for(int w = 0; w < def.length; w++){

System.out.println(def[w]);

}

}

}

EDIT: says out of bounds at line 14 and I don't see why

Message was edited by:

seithex

seithexa at 2007-7-21 21:49:26 >

The actual error message said something about "ArrayIndexOutOfBounds" and it refered you to this line:def[i] = ("The Number " + abc[i] + " appears " + count + "times");

In general you get this exception when (a) the index i is negative or (b) the index i is too big for the array.

Now i is never negative, so it's a case of the array index getting too big.

How big can i get? (Ie, what is the largest value i ever has?) Do the two array expressions - def[i] and abc[i] - make sense for this value of i?

pbrockway2a at 2007-7-21 21:49:26 >

One other piece of advice. You can get quick fixes here in the forum, but as a general rule, you're best sweating out most of this coding and debugging alone. I suggest that if you have a specific question that desperately needs answering, you ask it here in the forum, but then you close your internet browser and work, study, change, play, and otherwise torment your code for a good bit of time, at least 12 hours or more.

In other words: You have to work most of this out yourself in order for you to fully understand and appreciate it. Plus you'll get that sense of satisfaction when something finally goes right because of your own intelligence and perseverence. It's the same feeling that hooked most of us into coding in the first place.

petes1234a at 2007-7-21 21:49:35 >