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Why this error of sorting occuring only in cases of >5 table elements?

please see my code for BubbleSorting. When I choose 5 or more numbers for my table to be sorted I get an error:
at first.firstt.sorting_v2.sorting(sorting_v2.java:35).
Completely do not know why it occured, when I choose 2 or three element to sort it works perfect.
I know it can be made different way, this type of sorting but please show me what I did wrong as still learn and I'm very curious about the details of this error hmm.
Also see the image below:enter image description here
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("Choose how much number you want to sort:");
int sizeOfTab = scanner.nextInt();
int[] numbers = new int[sizeOfTab];
for (int i = 0; i < sizeOfTab; i++) {
System.out.println("Choose number to collection: ");
numbers[i] = scanner.nextInt();
}
scanner.close();
System.out.println(Arrays.toString(sorting(numbers)));
}
private static int[] sorting(int[] numbers) {
boolean notDone = false;
for (int i = 0; i < numbers.length - 1; i++) {
for (int j = 1; j < numbers.length; j++) {
if (numbers[i] > numbers[j]) {
int tmp = numbers[j];
numbers[j] = numbers[i];
numbers[i] = tmp;
notDone = true;
}
}
}
return notDone ? sorting(numbers) : numbers;
}
}

Your logical error is that you are always restarting your second inner loop from j = 1 aka the second element in
for (int j = 1; j < numbers.length; j++) { ... }
You only ever want to compare numbers[i] > numbers[j] for cases where j is greater than i.
Lets say you have the array [1, 2, 3, 4]
Currently your loop will run and reach a point where it will check numbers[2] > numbers[1] and switch the second and third element despite the array already being sorted.
To fix this simply always have your second loop start from the current value of i with 1 added:
for (int j = i+1; j < numbers.length; j++) { ... }

Java - 2D arrays, checking for duplication

The variable "num" is a 2D array. I'm trying to check in that array, if there are any duplicates. "num" is a user-input.
I have extensively looked through Java documentation and asked my lectures and I can't get a working answer. I understand the concept, what I'm meant to do, but just can't get the coding right.
Here is my code:
for(int i = 0; i < 3; i++){ //3 rows with 5 numbers each
for(int j = 0; j < 5; j++){
num[i][j] = Integer.parseInt(JOptionPane.showInputDialog(null, "Enter value for line: " + i + " and position: "+ j ));
if((num[i][j] == num[i][0]) || (num[i][j] == num[i][1]) ||(num[i][j] == num[i][2]) || (num[i][j] == num[i][3]) || (num[i][j] == num[i][4])){
if(num[i][j] != 0){
num[i][j] = Integer.parseInt(JOptionPane.showInputDialog(null, "ERROR. Enter value for line: " + i + " and position: "+ j ));
}
}
}
}
I have also tried using HashSet, but I think that only works with 1D arrays.
I would like to use something like this, as I feel this I understand the most:
secret = new Random().ints(1, 40).distinct().limit(5).toArray();
But obviously not with Random.
I've tried this:
Set<Integer> check = new HashSet<>();
Random gen = new Random();
for(int i = 0; i < 3; i++){ // 3 rows, 5 numbers
for(int j = 0; j < 5; j++){
num[i][j] = Integer.parseInt(JOptionPane.showInputDialog(null, "Enter value for row " + i + " and position " + j));
check.add(gen.nextInt(num[i][j]));
}
}
This last section of coding (directly above this) compiles and runs, but doesn't check for duplicates.

There are alternative ways to checking for duplicates (e.g. you could loop back through the data you've entered previously into the 2D array in order to check for duplicate values) however here's how I'd go about using a Set to check for duplicates in order to, Are you trying to populate the 2d array with all unique values, where each value is from the user?? (also - knowing this explicitly in the original post would be very helpful, thanks to Michael Markidis for specifying that)
With a little UX knowledge here, separating the ERROR is def helpful to the end-user, as ERROR + re-input at the same time is confusing.
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import javax.swing.JOptionPane;
public class App {
public static void main(String[] args) {
int[][] num = new int[3][5];
System.out.println("Before:");
for (int i = 0; i < 3; ++i)
System.out.println(Arrays.toString(num[i]));
Set<Integer> data = new HashSet<Integer>();
for (int i = 0; i < 3; i++) { // 3 rows with 5 numbers each
for (int j = 0; j < 5; j++) {
boolean isGoodInput = false;
while (!isGoodInput) {
String input = JOptionPane.showInputDialog(null, "Enter value for line: " + i + " and position: " + j);
Integer n = Integer.parseInt(input);
if (data.contains(n)) {
JOptionPane.showMessageDialog(null, "ERROR: Try again");
} else {
num[i][j] = n;
isGoodInput = data.add(n);
}
}
}
}
System.out.println("After:");
for (int i = 0; i < 3; ++i)
System.out.println(Arrays.toString(num[i]));
}
}
Note: the 2D array is limited to your specification in the original post as a 3x5, so you'd have to change these values in multiple places to make different sized arrays - perhaps making these more dynamic could speed up further development of this application in the future.

Here's one way to accomplish this where you use the hashset to track what has already been inserted into the 2D array:
int[][] num = new int[3][5];
Set<Integer> check = new HashSet<>();
for (int i = 0; i < 3; i++)
{ // 3 rows, 5 numbers
for (int j = 0; j < 5; j++)
{
int n = 0;
do
{
n = Integer.parseInt(JOptionPane.showInputDialog(null, "Enter value for row " + i + " and position " + j));
} while (!check.add(n)); // keep looping if it was in the hashset
// add it to the array since we know n is not a duplicate at this point
num[i][j] = n;
}
}

For loop with if inside not working

I am having with my studies, I have problem where I am supposed to get an IP address from an user and then iterate it from right most number and if that number will be equal or more than 256 then I should iterate the number -1 place before this and this one set to 0.
I tried to solve it by simply making primitive code at first which would do it one time and only by user input and after that I would add more complexity like original more than one iteration, error checks and put code into propper .java files and classes.
I understand that this would be better with ArrayList but I intended to add ArrayList instead of simple Array later.
Could anyone please tell me why the loop with condition put outofarraybound exception when I am not trying to iterate "i"?
for (i = 3; i >= 0; i--) {
pomoc = zasobnikIPadresa[i];
if (pomoc > 255) {
zasobnikIPadresa[i] = 0;
zasobnikIPadresa[i-1] = pomoc + 1;
}
}
So far I was able to analyze that I dont have proper knowledge of Arrays and I think that solution to my issue would help me to finish my problem and to better understand them.
here is full code so far:
package com.ipadresa.classes;
import java.util.Scanner;
public class Hlavni {
public static void main(String[] args) {
int i = 0;
int[] zasobnikIPadresa = new int[4];
Scanner ctecka = new Scanner(System.in);
for (i = 0; i < zasobnikIPadresa.length; i++) {
zasobnikIPadresa[i] = ctecka.nextInt();
}
System.out.print("Original IP adress: ");
for (i = 0; i < zasobnikIPadresa.length; i++) {
if (i < zasobnikIPadresa.length - 1) {
System.out.print(zasobnikIPadresa[i] + ".");
} else {
System.out.print(zasobnikIPadresa[i]);
}
} System.out.println();
int pomoc = 0;
for (i = 3; i >= 0; i--) {
pomoc = zasobnikIPadresa[i];
if (pomoc > 255) {
zasobnikIPadresa[i] = 0;
zasobnikIPadresa[i-1] = pomoc + 1;
}
}
System.out.print("Final IP adress: ");
for (i = 0; i < zasobnikIPadresa.length; i++) {
if (i < zasobnikIPadresa.length - 1) {
System.out.print(zasobnikIPadresa[i] + ".");
} else {
System.out.print(zasobnikIPadresa[i]);
}
}
ctecka.close();
}
}

Since by this for loop condition, for (i = 3; i >= 0; i--) {, the variable i is allowed to == 0, then let's see what the array index is here when i is 0:
zasobnikIPadresa[i-1] = pomoc + 1;
it's -1. Ouch.

What if the condition
pomoc > 255
is true when
i==0.
Then you'll be accessing zasobnikIPadresa[-1] i.e. out of bound.

Can't find five lowest values in an array...max works while min array is not assigned values

I'm very close to completing this, all I need is help on finding the five lowest values from a text file by using arrays. I figured out how to find the five highest values, but my min array to find the lowest values always outputs five 0's.
Output: //obviously dependent on individual text file
Total amount of numbers in text file is 10
Sum is: 1832
1775 14 9 9 7 //max
0 0 0 0 0 //min
Any help is much appreciated!
import java.util.Scanner;
import java.io.*;
public class HW3
{
public static void main(String[] args) throws IOException
{
File f = new File("integers.txt");
Scanner fr = new Scanner(f);
int sum = 0;
int count = 0;
int[] max = new int[5];
int[] min = new int[5];
int temp;
while(fr.hasNextInt())
{
count++;
fr.nextInt();
}
Scanner fr2 = new Scanner(new File("integers.txt"));
int numbers[] = new int[count];
for(int i=0;i<count;i++)
{
numbers[i]=fr2.nextInt(); //fills array with the integers
}
for(int j:numbers)//get sum
{
sum+=j;
}
for (int j=0; j < 5; j++) //finds five highest
{
for (int i=0; i < numbers.length; i++)
{
if (numbers[i] > max[j])
{
temp = numbers[i];
numbers[i] = max[j];
max[j] = temp;
}
}
}
for (int j=0; j < 5; j++) //finds five lowest...array not assigned values
{
for (int i=0; i < numbers.length; i++)
{
if (numbers[i] < min[j])
{
temp = numbers[i];
numbers[i] = min[j];
min[j] = temp;
}
}
}
System.out.println("Total amount of numbers in text file is " + count);
System.out.println("Sum is: " + sum);
System.out.println(max[0] + " " + max[1] + " " + max[2] + " " + max[3] + " " + max[4]);
System.out.println(min[0] + " " + min[1] + " " + min[2] + " " + min[3] + " " + min[4]);
}
}

Your min array will be initialized with zero values. So the values in numbers will always be higher (assuming there are no negatives).
I'd suggest that you initialize min[j] with numbers[0] before the inner loop.
for (int j=0; j < 5; j++) //finds five highest
{
min[j] = numbers[0]; // Add this line
for (int i=0; i < numbers.length; i++)
{

Try debugging your code by entering inside your nested min loop the following line:
System.out.println("the value of numbers[i] is: " + numbers[i]);
so it looks like this:
for (int j=0; j < 5; j++) //finds five lowest...array not assigned values
{
for (int i=0; i < numbers.length; i++)
{
if (numbers[i] < min[j])
{
System.out.println("the value of numbers[i] is: " + numbers[i]);
temp = numbers[i];
numbers[i] = min[j];
min[j] = temp;
}
}
}
You'll notice something interesting. The innermost nested part doesn't even start.
Try putting that line into the nested max loop in its respective location instead... and it will run fine and show the max array values. You are getting zero values for the min array because (other than initial assigning) the innermost part of the nested min loop isn't being started somehow, so it fails to run and searched values do not get assigned to the min array.
The outer nested parts of the min loop run fine if you try debugging them with a similar line. It's this part that won't start and something's wrong with:
if (numbers[i] < min[j])
{
System.out.println("the value of numbers[i] is: " + numbers[i]);
temp = numbers[i];
numbers[i] = min[j];
min[j] = temp;
}
(Update)
In the min loop, numbers[i] from i=0 to i=4 have a value of 0 after completing the max loop.
You only need to add one line and use int i=5 instead of int i=0 inside your min loop:
for (int j=0; j < 5; j++) //finds five lowest...array not assigned values
{
min[j] = max[4]; // added line
for (int i=5; i < numbers.length; i++) // change to int i=5
{
if (numbers[i] < min[j])
{...

As the other answer states, your problem is that you did not take into account the arrays beginning at 0. In Java, it sets default values for that data structure. For primitives, this will normally be 0 or false. However, when you move into data structures, you will have problems with null pointer exceptions if you fail to initialize your objects. For this reason, I would urge you to get into the habit of setting the values in your data structures before you ever use them. This will save you A LOT of debugging time in the future.
If you know the values in advance, you can set them manually with {0,0,0,0,0} notation, or your can initialize using a for loop:
for(int i = 0; i < array.length; i++)
array[i] = init_value;
I would recommend that you also look into trying to consolidate as much as possible. For example, in your code you go through the same data 4 times:
1) read the integers from the file into an integer array
2) sum all of the numbers in the integer array
3) look for max
4) look for min
I'm not sure if you've covered functions yet, but one example of consolidating this might look like:
while(fr2.hasNextInt()){
int i = fr2.nextInt();
sum += i;
checkHighest(i);
checkLowest(i);
}
You then define these functions and put the meat elsewhere. This lets you only worry about the loops in one place.

You have 2 problems.
First was explained by Tom Elliott.
The second problem is that also the max[] array is initialized with 0, and when you search for max values you change the value from max array (which is 0) with the value from the numbers array, so the numbers array becomes filled with 0s.
A quick solve (though not the best) would be to copy the numbers array in a temp array and use that temp when searching for min values.
In case you didn't exactly understood what I said, try to make a print of the numbers array after you found the 5 max values.

Just curious , Cant you just sort it(using quick sort) select top five and bottom five ?
- if you can use sorting I think this should work then
int sum = 0;
int count = 0;
int[] max = {Integer.MIN_VALUE,Integer.MIN_VALUE,Integer.MIN_VALUE,Integer.MIN_VALUE,Integer.MIN_VALUE};
int[] min = {Integer.MAX_VALUE,Integer.MAX_VALUE,Integer.MAX_VALUE,Integer.MAX_VALUE,Integer.MAX_VALUE};
int temp;
int visited[] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
for (int j : numbers)// get sum
{
sum += j;
}
int tempindex;
for (int j = 0; j < 5; j++) // finds five highest
{
for (int i = 0; i < numbers.length; i++) {
if (visited[i] != 1) {
if (numbers[i] > max[j]) {
max[j] = numbers[i];
tempindex = i;
}
}
}
visited[tempindex] = 1;
}
for (int j = 0; j < 5; j++) // finds five lowest...array not assigned
// values
{
for (int i = 0; i < numbers.length; i++) {
if (visited[i] != 1) {
if (numbers[i] < min[j]) {
min[j] = numbers[i];
tempindex = i;
}
}
}
visited[tempindex] = 1;
}

How to print statement outside loop to avoid duplicates?

I would like my print statement to be outside the loop so the statement doesn't print the same thing over and over. The for loop below simply checks a number from one array against another to find out how many matches have been found. Defining the variables above and printing the statements below results in a "variable not initialised error" which is understandable.
for (int i = 0; i < 6; i++)
{
int chkNum = myArray[i];
int lottMtch = count(chkNum, rndNum);
if (lottMtch > 0)
{
System.out.println(lottMtch + "matches found");
System.out.print(chkNum);
}
else {
System.out.print("no matches found");
}
}

Declare the variable before the loop and then do your stuff in the loops, like adding one to the variable if it is found, then print it out afterwards if it is more than 0. Something like this...
int var = 0;
for(...) {
if(found)
var++;
}
if(var > 0)
sysout(var);
Of course this code won't work but it is a start. For your learning experience I will let you implement this idea with your code.

this would not really make sense ..
if you want than Try this ...
int lottMtch[]=new int[myArray.length];
Arrays.fill(lottMtch, 0);
for (int i = 0; i < 6; i++)
{
int chkNum = myArray[i];
lottMtch[i] = count(chkNum, rndNum);
}
for (int i = 0; i < 6; i++)
{
if (lottMtch[i] > 0)
System.out.println(lottMtch[i] + " matches found "+ myArray[i]);
}
If you wan to found just how many match of rndNum in myArray Than try this
Here i assume rndNm is global
int lottMtch=0;
for (int i = 0; i < 6; i++)
{
lottMtch += count(myArray[i], rndNum);
}
if (lottMtch> 0)
System.out.println(lottMtch + " matches found "+ rndNum);
As per discussed in comment Try this ..
Map<Integer,Integer> map = new HashMap<Integer,Integer>();
for (int i = 0; i < 6; i++)
{
Integer chkNum = myArray[i];
Integer cnt = (Integer)count(myArray[i], rndNum);
if(cnt>0)
{
if(map.get(chkNum)==null)
map.put(chkNum,1);
else
map.put(chkNum, map.get(chkNum)+1);
}
}
for (Object key : map.keySet())
System.out.println(map.get(key) + " matches found "+key.toString());

This is because if you only declare the variables above the loop and only initialize said variables in the loop, when you attempt to print them outside of the loop, there's no guarantee that they would have been initialized.
So, perhaps you want something like this:
int lottMtch = 0;
for (int i = 0; i < 6; i++)
{
int chkNum = myArray[i];
lottMtch += count(chkNum, rndNum);
//System.out.print(chkNum); this would not really make sense outside of the loop
}
if (lottMtch > 0)
{
System.out.println(lottMtch + "matches found");
}
else
{
System.out.print("no matches found");
}

You need to declare a variable outside the loop if you plan to access it after the loop exits.

You need to initialise variables outside the loop. Try this:
int chkNum = 0;
int lottMtch = 0;
for (int i = 0; i < 6; i++)
{
chkNum = myArray[i];
lottMtch = count(chkNum, rndNum);
}
if (lottMtch > 0)
{
System.out.println(lottMtch + "matches found");
System.out.print(chkNum);
}
else {
System.out.print("no matches found");
}