I will have a series of random arrays similar to.
array1[] = {1,2,3,0,0,5,6}
array1[] = {1,2,0,0,4,5,6}
I want them to end up like, so I replace the first 0 with X.
array1[] = {1,2,3,X,0,5,6}
array1[] = {1,2,X,0,4,5,6}
the code I'm using replaces all zeroes giving instead of just one.
array1[] = {1,2,3,X,X,5,6}
array1[] = {1,2,X,X,4,5,6}
Which isn't what I'm looking for. I'd be happy just replacing either one but only one.
The code I'm using,
for(int i=0; i<array.length; i++){
if(fruit[i] == 0)
fruit[i]=X;
}
Hope that was clear, thanks for any help! Being stuck at this for a little while now.
Try using break.
for(int i = 0; i < array.length; i++) {
if(fruit[i] == 0) {
fruit[i] = X;
break;
}
}
This will ensure only one is changed, max.
Related
I would like to know how array[array[i]]++ works in java.
I wrote the code, and want to know how this count integer array is working here
int[] counts = new int[201];
for (int i = 0; i < d; i++) {
counts[array_inside[i]]++;
}
and
also would like to know if i does like below how count array values will be written and left or right shift its values
for(int i = j; i < array_inside.length; i++){
count[array_inside[i-j]]--;
count[array_inside[i]]++;
}
Consider it as two operations (because it is). This
counts[array_inside[i]]++;
is equivalent to
int p = array_inside[i];
counts[p]++;
I'm trying to get a string to read a file, that then stores all the digits in an array that can be recalled one by one in another loop. Name the array digitStorage please :D Here's my current bit of code:
for (int i = 0; i <= 40000 ; i++) {
String digit;
if ( i <=39998)
digit = pictureFile.substring(i, i+1);
else
digit = pictureFile.substring(39998,39999);
My question :
What to do, how could I do this, how would I get it to read each digit (single integers) 1 by 1 and then store them 1 by 1 in an array that could be later recalled, each number corresponds to a color that would be used to sketch a picture in a graphics window (there are 40,000 single digit integers in a file that i've already worked out how to read) ?
Cheers.
As you have mentioned that you have already read the file and you want to store it in some kind of array. Below code will work.
List<String> list = new ArrayList<String>();
for (int i = 0; i <= 40000 ; i++) {
String digit;
if ( i <=39998)
list.add(pictureFile.substring(i, i+1));
else
list.add(pictureFile.substring(39998,39999));
}
If you want List of Integer then us.
List<Integer> list = new ArrayList<Integer>();
for (int i = 0; i <= 40000 ; i++) {
String digit;
if ( i <=39998)
list.add(Integer.parseInt(pictureFile.substring(i, i+1)));
else
list.add(Integer.parseInt(pictureFile.substring(39998,39999)));
}
You can iterate through list after this.
Your question is not very clear, but I believe this should do it:
int [] digitStorage = new int[40000];
for (int i = 0; i <= 40000 ; i++) {
if ( i <=39998)
int[i] = Integer.parseInt(pictureFile.substring(i, i+1));
else
int[i] = Integer.parseInt(pictureFile.substring(39998,39999));
Based on your comments and question, the easiest solution I can think of is to use String.toCharArray() and Character.digit(char, int) like
char[] chars = pictureFile.toCharArray();
int[] digitStorage = new int[chars.length];
for (int i = 0; i < chars.length; i++) {
digitStorage[i] = Character.digit(chars[i], 10);
}
System.out.println(Arrays.toString(digitStorage));
Just to keep my skills sharp, I decided to write a small programme that prints out the values of an array, after being given two variables that each contain a different value.
My expectation was that each value would show onscreen, but this did not happen. Instead, only the last element's value was displayed onscreen (in the code below, being the number "2" --> That is an integer, not a string).
Why is this?
Also, why does dynamic initialisation produce the result I wish, but not the way I do it in the code?
Many thanks.
int[] arrayOne;
arrayOne = new int[2];
int numOne = 1;`
int numTwo = 2;`
for (int i = 0; i < arrayOne.length; i++) {`
arrayOne[i] = numOne;
arrayOne[i] = numTwo;
System.out.println(arrayOne[i]);
}
If you want to put the values of two variables into an array, you need to use two assignments:
arrayOne[0] = numOne;
arrayTwo[1] = numTwo;
Now you can use a for loop to print out the contents of the array.
This kind of defeats the purpose of using an array, though.
You're setting different values to same location, causing only last value to be saved.
Your code similar to doing:
arrayOne[0] = 1;
arrayOne[0] = 2;
After these two lines, arrayOne[0] will hold the value of 2.
If you want to put these two values, you need to put them in different places:
arrayOne[0] = 1;
arrayOne[1] = 2;
In Java (and in almost any language I know), an array can only contain one vale per cell i.e. if you do "array[i] = 1" and after "array[i] = 2" , then the i-cell will CHANGE its value from 1 to 2, not append the value 2 after the 1. In the end, youre array will contain numTwo in every single cell.
If you want to initialize the array with a different value in each cell, I'm afraid you need to do it manually, not using the loop.
You need to do the population of your array before you iterate through it with the loop.
arrayOne[0] = numOne;
arrayOne[1] = numTwo;
Then do your loop:
for (int i = 0; i < arrayOne.length; i++)
{
System.out.println(arrayOne[i]);
}
Many ways to initialize an array...
int[] a = new int[2];
a[0] = 1;
a[1] = 2;
Or:
int[] a = new int[2];
for( int i = 0; i < a.length; i++ ){
a[i] = i + 1;
}
Or:
int[] a = new int[]{ 1, 2 };
Or.
int valOne = 1;
int valTwo = 2;
int[] a = new int[]{ valOne, valTwo };
Take care when you see more than one assignment to the same array element in a loop as you have it before the println. Is this what you want? The second one wins and sets the current (i-th) element to 2.
You need to do something like this:
public class demo{
private static int i = 0;
private static int[] demo = new int[10];
public static void main(String[] args){
for(int i = 0; i < 10; i++){
addElementToArray(i);
}
for(int i = 0; i < demo.length; i++){
System.out.println(demo[i]);
}
addElementToArray(i);
}
public static void addElementToArray(int input){
try{
demo[i] = input;
i++;
}catch(ArrayIndexOutOfBoundsException e){
e.printStackTrace();
}
}
}
Don't set the values inside the for-loop either, that is (imo) plain stupid, for what you are trying to achieve
I'm trying to add some elements into an array with this void method;
if (count == numbers.length) {
int[] temp = new int[count+1];
for(int a = 0; a<count; a++)
temp[a] = numbers[a];
numbers = temp;
numbers[count] = (x);
count++;
It doesnt add. Thank for your attention.
Two most likely reasons for this to not work are:
count does not equal numbers.length;
x does not contain the number to be added.
Other than the slightly odd indentation and the missing closing brace the code looks fine.
P.S. Instead of managing the storage by hand you might want to look into using ArrayList<Integer>.
Im trying to add an element to an array at its last position in Java, but I am not able to...
Or rather, I don't know how to. This is the code at the moment:
String[] values = split(line, ",");
int[][] coordinates = new int[2][values/2];
for(int i = 0; i < values.length; i++) {
if(i % 2 == 0) { //THIS IS EVEN VALUES AND 0
coordinates[0][coordinates[0].length] = values[i];
} else { //THIS IS ODD VALUE
coordinates[1][coordinates[1].length] = values[i];
}
}
EDITED VERSION:
String[] values = split(line, ",");
int[][] coordinates = new int[2][values/2];
int x_pos = 0;
int y_post = 0;
for(int i = 0; i < values.length; i++) {
if(i % 2 == 0) { //THIS IS EVEN VALUES AND 0
coordinates[0][x_pos] = values[i];
x_pos++;
} else { //THIS IS ODD VALUE
coordinates[1][y_pos] = values[i];
y_pos++;
}
}
values is being read from a CSV file. My code is I believe wrong, since it will try to add the values always at the maximum array size for coordinates[] in both cases.
How would I go around adding them at the last set position?
Thanks!
/e: Would the EDITED VERSION be correct?
Your original code has two problems:
it addresses the array badly, the las element in a Java array is at position length-1, and this would result in an ArrayOutOfBoundsException
even if you'd correct it by subtracting 1, you would always overwrite the last element only, as the length of a Java array is not related to how many elements it contains, but how many elements it was initialised to contain.
Instead of:
coordinates[0][coordinates[0].length] = values[i];
You could use:
coordinates[0][(int)Math.round(i/2.0)] = values[i];
(and of course, same with coordinates[1]...)
EDIT
This is ugly of course:
(int)Math.round(i/2.0)
but the solution I'd use is far less easy to understand:
i>>1
This is a right shift operator, exactly the kind of thing needed here, and is quicker than every other approach...
Conclusion: this is to be used in a live scenario:
Use
coordinates[0][i>>1] = values[i];
EDIT2
One learns new things every day...
This is just as good, maybe a bit slower.
coordinates[0][i/2] = values[i];
If you know you'll definitely have an even number of values you can do
for(int i = 0; i < values.length / 2; i++) {
coordinates[0][i] = values[2*i];
coordinates[1][i] = values[2*i + 1];
}
You have to store the last position somewhere. .length gives you the size of the array.
The position in the array will always be the half of i (since you put half of the elements in one array and the other half in the other).
String[] values = split(line, ",");
int[][] coordinates = new int[2][values/2];
for(int i = 0; i < values.length; i++) {
if(i % 2 == 0) { //THIS IS EVEN VALUES AND 0
coordinates[0][ i / 2] = values[i];
} else { //THIS IS ODD VALUE
coordinates[1][ i / 2 + 1 ] = values[i];
}
}
The array index for java is from "0" to "array length - 1".
http://docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html
Each item in an array is called an element, and each element is accessed by its numerical index. As shown in the above illustration, numbering begins with 0. The 9th element, for example, would therefore be accessed at index 8.
why not:
String[] values = split(line, ",");
int[][] coordinates = new int[2][values/2];
for(int i = 0; i < values.length; i+=2) {
coordinates[0][i/2] = values[i];
coordinates[1][i/2] = values[i+1];
}