This is my current code:
public static void main(String[] args) {
int [][] twoD = new int [5][5];
/*for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
System.out.print(twoD[i][j] + "");
}
}*/
}
}
I can't seem to do it. I got confused and I removed the part of testing w/commenting. Just ignore that.
I am aiming to get a two dimensional array like this:
1 2 3 4 5
2 4 6 8 10
3 6 9 12 15
4 8 12 16 20
5 10 15 20 25
However, I just don't get it. How can I get that result? I'm a beginner at java.
First, you need to populate the array with data, and you forgot System.out.println for each row of the array.
int [][] twoD = new int [5][5];
// populate array with data
for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
twoD[i][j] = (j+1)*(i+1);
}
}
// print result
for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
System.out.print(twoD[i][j]);
System.out.print(" ");
}
System.out.println();
}
You have to populate the data as well:
int[][] arr = new int [5][5];
for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
arr[i][j] = (j+1)*(i+1);
}
}
And the code to print would be:
for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
System.out.print(arr[i][j] + " ");
}
System.out.println();
}
You are doing fine, you just need to put line jump System.out.println(); every time the second for ends
for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
System.out.print(twoD[i][j] + " ");
}
System.out.println();
}
You are on the right track, that for loop will print out the array like that, all you need to do is print a new line character after finishing the for(j) loop. But, at least in the snippet you posted, you aren't actually doing any assignments, so there aren't any values in your array to print, Java will initialize all ints to zero for you.
The array doesn't just automatically populate with incrementing integers, rather each cell of the array will automatically initialized to 0, you have to set the values you want the array to contain. You can use the concept of your testing class to do this if you wish, just set each cell of the 2D array to a certain value. After that, you can print out the array, making sure to print a each row of the array on a new line. For instance:
public static void main(String[] args) {
int [][] twoD = new int [5][5];
int increment = 1;
for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
twoD[i][j] = increment++;
}
}
for(i = 0; i<5; i++){
for(j = 0; j<5; j++){
System.out.print(twoD[i][j] + " ");
}
System.out.println();
}
}
The first set of nested for loops will set each of the cells of the 2D array to the incremented integers you want (note increment++ will first set the cell to the value increment currently is, then add one to the variable). The second set of nested for loops will print out the array as you desire.
refer this code
int[][] twoD = new int[5][5];
// add values to array
for (int i = 0; i < 5; i++) {
int val = 1;
val = val + i;
for (int j = 0; j < 5; j++) {
twoD[i][j] = val * (j + 1);;
}
}
// Print array
for (int i = 0; i < 5; i++) {
for (int j = 0; j < 5; j++) {
System.out.print(twoD[i][j] + " ");
}
System.out.println();
}
as others pointed out you need to print it nicely to see the pattern, i and j are indices of your array. However, I see that you have a nice pattern so just running two loops won't solve the problem.
Maybe something like this would help (not giving exact answer intentionally)
int [][] twoD = new int [5][5];
int i;
// initialize
int c = 1; int j = 0;
for(c=1; c<5; c++) {
for( i = 1; i<=5; i++){
twoD[i-1][c-1] = c*c*i; twoD[c-1][i-1]=c*c*i;
}
}
for( i = 0; i<5; i++) {
for( j = 0; j<5; j++) {
System.out.print(twoD[i][j]);System.out.print(" " );
}
System.out.println("\n");
}
Related
I have to print the following numbers using nested loops, and I kinda have an idea how, but not how to execute it.
000111222333444555666777888999
000111222333444555666777888999
000111222333444555666777888999
My code so far is something like:
public class opgave_2 {
public static void main(String[] args) {
final int first = 3;
final int second = 3;
final int third = 9;
for (int i = 0; i <= first ; i++) {
for (int j = i; j <= second; j++) {
for (int k = j; k <= third; k++) {
System.out.print(i);
}
}
}
}
}
You should proceed by steps to resolve such problem.
First, you want to print a number 3 times :
int myNumber = 0;
for(int i=0; i<3; i++) {
System.out.print(myNumber);
}
Second, you want to repeat it 9 times and your number to vary from 0 to 9 (seems like an index of loop) :
for(int myNumber=0; myNumber<=9; myNumber++) {
for(int i=0; i<3; i++) {
System.out.print(myNumber);
}
}
Third, you want to display this line 3 times :
for(intj=0; j<3; j++) {
for(int myNumber=0; myNumber<=9; myNumber++) {
for(int i=0; i<3; i++) {
System.out.print(myNumber);
}
}
System.out.println(""); //new line
}
What about something like this:
for (int i = 0; i < 3; i++) {
for (int j = 0; j <= 9; j++) {
System.out.printf("%1$s%1$s%1$s", j);
}
System.out.println();
}
Which uses 2 nested loops. The first to print the line 3 times, and the second to print the numbers per line
you can use a loop, that loops 3 times. in that you put a loop that prints every number from 0 to 9 3 times in a row within the same line
for(int a = 0; a < 3; a++){
for(int i = 0; i < 10; i++){
System.out.print(i+""+i+""+i);
}
System.out.println(); //for the new line
}
or
for(int a = 0; a < 3; a++){
for(int i = 0; i < 10; i++){
System.out.print(i);
System.out.print(i);
System.out.print(i);
}
System.out.println(); //for the new line
}
this should do
Im doing some personal work, and I am using this array that I thought of, but I cant figure out whats the array is after the code stops running.
int cnt = 0;
int[][] numarray = new int[2][3];
for(int i = 0; i < 3; i++) {
for(int j = 0; j< 2; j++) {
numarray[j][i] = cnt;
cnt++;
}
}
I am pretty sure that it ends at [2][1] but I am not 100% sure of it
Just tried this code:
int cnt = 0;
int[][] numarray = new int[2][3];
for(int i = 0; i < 3; i++) {
for(int j = 0; j< 2; j++) {
numarray[j][i] = cnt;
cnt++;
System.out.print(numarray[j][i]+" ");
}
System.out.println("");
}
and got this result:
0 1
2 3
4 5
The 'cnt' is incremented by 1 for each iteration. That's why you have 0,1,2,3,4,5.
Also learn how to use debugger in an IDE, you can then explore the value of i, j, cnt by yourself.
why don't you try this?
int cnt = 0;
int[][] numarray = new int[2][3];
for(int i = 0; i < 3; i++) {
for(int j = 0; j< 2; j++) {
numarray[j][i] = cnt;
System.out.println(String.format("array[%d[%d]=%d",j,i,numarray[j][i]));
cnt++;
}
}
you can iterate the array after code finish
for(int i = 0; i < 2; i++) {
for(int j = 0; j< 3; j++) {
System.out.print(numarray[i][j]+" ");
}
System.out.println();
}
summary: cnt is incremented by 1 for each iteration in the inner for loop.
cnt is being incremented by 1 i.e. cnt++ is same as cnt = cnt + 1;
so count values increment from 0 i.e. 0,1,2,3,4,5... Also note, the value of cnt is assigned to the array being created, where you have numarray[j][i] = cnt;
You can simply printout the value using System.out.println(cnt);
I want to flip 5 coins as a group - 1024 times and count how many tails i get. However i am getting ArrayIndexOutOfBoundsException: 4 error.
Is this because j in the second loop is not reset when the first loop runs its first time? If so, how would i go about this then?
public class Q2 {
public static void main(String[] args) {
int totalTails, totalHeads;
int coin[];
coin = new int[4];
totalHeads = 0;
totalTails = 0;
for (int i = 0; i < 1024; i++) {
for (int j=0; i<5; j++){
coin[j] = 1 + (int) (Math.random() * (2 - 1 + 1));
if (coin[j] == 1) {
totalHeads++;
}
else {
totalTails++;
}
}
}
System.out.println("Number of tails were obtained = " + totalTails);
System.out.println("Number of heads were obtained = " + totalHeads);
}
}
for (int j=0; i<5; j++){
It should be j<5
coin = new int[4];
It should be int[5]
Change this line:
for (int j=0; i<5; j++){
To this line:
for (int j=0; j<4; j++){
You are going out of bounds on coin
It would be even better if you use length property. Like th
for (int j=0; j<coin.length; j++){
please change for (int j=0; i<5; j++) to for (int j=0; j<5; j++) and your code should work fine.
int[][] input = new int[3][];
int count = 1;
for(int i = 0; i <= 2 ; i++ ) {
for(int j = 0; j <= 2; j++) {
input[i][j] = count++;
}
}
Fifth line throws an error.
Second dimension of the array is empty.
int[][] input = new int[3][];
Try this:
int[][] input = new int[3][3];
int[][] input = new int[3][];
this type of array are called ragged array.
in you have to define the size of column for each row. like this:
input[0]=new int[2];//for row 1 (row 1 contain 2 column)
input[1]=new int[5];//for row 2 (row 2 contain 5 column)
input[2]=new int[1];// for row 3 (row 3 contain 1 column)
so define column size for each row as you wish
/*Ragged Arrays
are multidimensional arrays in which
the rows have different no of cols.
*/
class Ragged
{
public static void main(String args[])
{
//declaration of a ragged array
int arr[][] = new int[3][];
//declaration of cols per row
arr[0] = new int[4];
arr[1] = new int[2];
arr[2] = new int[3];
int i, j;
for(i =0; i< arr.length; i++)
{
for(j =0 ; j< arr[i].length; j++)
{
arr[i][j] = i + j+ 10;
}
}
for(i =0; i< arr.length; i++)
{
System.out.println();//skip a line
for(j =0 ; j< arr[i].length; j++)
{
System.out.print(arr[i][j] + " ");
}
}
//-------------more----------------
int temp[];//int array reference
//swap row2 and row3 of arr
temp = arr[1];
arr[1] = arr[2];
arr[2] = temp;
System.out.println();//skip a line
for(i =0; i< arr.length; i++)
{
System.out.println();//skip a line
for(j =0 ; j< arr[i].length; j++)
{
System.out.print(arr[i][j] + " ");
}
}
}//main
}//class
/*
TO declare a ragged array define a
multi dimensional array with the val
of last dimension missing.
The explicitly define the size of
the last dimension for all the rows.
*/
You need to initialize the second dimension
1) int[][] input = new int[3][3];
or
2)
for(int i = 0; i <= 2 ; i++ ){
input[i] = new int[3];
}
Because you second array dimension is not specified.
This should run:
int[][] input = new int[3][3];
int count = 1;
for(int i = 0; i <= 2 ; i++ ){
for(int j = 0; j <= 2; j++){
input[i][j] = count++;
}
}
See executable example
Because you didn't specify the second dimension size.
You need specify size for second array during initialization.
Also you can use .length property of array to avoid hard coded sizes.
int[][] input = new int[3][3];
int count = 1;
for(int i = 0; i <= input.length ; i++) {
for(int j = 0; j <= input[i].length; j++) {
input[i][j] = count++;
}
}
I'm working on a program that requires me to take in a 1-D String array from a file and turn it into a 2-D array. Taking in the array from the file works fine, but I can't get the second part to work.
The code I'm working with is:
char[][] array2 = new char [7][5];
for (int i = 0; i < array1.length; i++)
{
array2[i]= array[i].toCharArray();
}
for (int i = 0; i < 5; i++)
{
for (int j = 0; j < 7; j++)
{
System.out.println(array2[i][j]);
}
}
The array is supposed to print in a grid format, but is printing downward.
Any help is appreciated, thanks.
Use print instead of println in inner loop and after each loop print a blank line with println.
for (int i = 0; i < 7; i++) // see changes 5/7. You did "new char[7][5]" not [5][7]
{
for (int j = 0; j < 5; j++) // see changes 7/5
{
System.out.print(array2[i][j]);
}
System.out.println();
}
Update:
Following is a program that convert String array to 2D char array.
public class StringToChar {
public static void main(String[] args) {
String[] strArr = { "HELLO", "WORLD" };
char[][] char2D = new char[strArr.length][];
for (int i = 0; i < strArr.length; i++) {
char2D[i] = strArr[i].toCharArray();
}
for (char[] char1D : char2D) {
for (char c : char1D)
System.out.print(c + " ");
System.out.println();
}
}
}
few suggestions,
replace char[][] array2 = new char [7][5]; with char[][] array2 = new char [array1.length][]; (where array1 holds your strings), so your 2d array will have as many rows as you have strings
your loop
for (int i = 0; i < 5; i++)
{
for (int j = 0; j < 7; j++)
....
}
change to
for (int i = 0; i < array2.length; i++)
{
for (int j = 0; j < array2[i].length; j++)
....
another thing is if you want your string printed in rows, use System.out.print, and whenever you finished inner loop, print out'\n' character
You are using println, which is why each character is printed on its own line. You must use print instead.
Note that your initialization with
new char [7][5];
doesn't work as you expect because the inner arrays will be overwritten. Use
new char[7][]
for the same result, but more clarity as to your intent. Here
for (int i = 0; i < 5; i++)
for (int j = 0; j < 7; j++)
you have apparently reversed the order of indices: you are iterating only through 5 outer arrays, but you have allocated 7. What you should do instead is check against the actual array length and not a hardcoded number. The inner array may be of any size, after all (it depends on the string length).
Have a look at the String.toCharArray()
If it is printing downwards then change
for (int i = 0; i < 7; i++) //row loop
{
for (int j = 0; j < 5; j++) //column loop
{
System.out.print(array2[i][j]);
}
System.out.println(); //add here
}
Have a look at
formatting
print vs println