I'm trying to figure out what's wrong with my code for printing the two dimensional array
int[][] container = new int [3][6];
for (int i = 0; i <= 3; i++) {
for (int j = 0; j <== 6; j++) {
System.out.print(contianer[i][j] + " ");
}
}
System.out.println();
<==is not an operator.
Array start from 0 to length - 1
you have a typo in your variable inside the for
System.out.println();must be executed inside the first for not outside.
int[][] container = new int [3][6];
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 6; j++) {
System.out.print(container[i][j] + " ");
}
System.out.println();
}
Related
hello guys I am struggling to find the right way to print only the even numbers of the array.
I made a 1 dimensionnal array to save the element of the columns and then make sure if the index of the col%2==0 put that number in the output.
import java.util.Scanner;
public class Matrix {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
//array with 3 row in 5 col
int[][] matrix = new int[3][5];
//int []y = new int[5];
// to impalement th array
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 5; j++) {
System.out.print("Enter matrix[" + i + "][" + j + "]: ");
matrix[i][j] = input.nextInt();
}
System.out.print("\n");
}
System.out.print("matrix values \n");
// to show up the originally array
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 5; j++) {
System.out.print(matrix[i][j] + "\t");
}
System.out.print("\n");
}
//////the new array to display only the even numbers in the col
System.out.print("\n");
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 5; j++) {
int[] y = matrix[j];
for (int k = 0; i < y.length; i++) {
if (y[k] % 2 == 0)
System.out.println(y[k]);
}
}
}
}
}
the output doesn't print the new array
matrix values
1 2 3 4 5
6 7 8 9 10
3 2 4 5 9
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 3 out of bounds for length 3
at Matrix.main(Matrix.java:43)
Replace i by k here :
for (int j = 0; j < 5; j++) {
int[] y = matrix[j];
for (int k = 0; i < y.length; i++) {
if (y[k] % 2 == 0)
System.out.println(y[k]);
}
}
Hi all my program consist of an 2 Dimension array,im reading 2 cordinates in a loop and triying to check if those cordinates in the array are alredy been filled with a asterisc,if this is true y want to re-enicialize my array with the default value "-", and if there is not an asterisc in that specified position y want to fill it in with a asterisc,im not sure if im going for the correct aproach.
this is part of my code.
thanks all.
String[][] matrix = new String[5][5];
String asterisc = "*";
String defaultValue = "_";
Scanner sc = new Scanner(System.in);
int a, b;
for (int i = 0; i < matrix.length; i++) {
for (int j = 0; j < matrix.length; j++) {
matrix[i][j] = defaultValue;
}
}
for (int i = 0; i < matrix.length; i++) {
for (int j = 0; j < matrix.length; j++) {
System.out.print(matrix[i][j] + "|");
}
System.out.println();
}
a = 0;
b = 0;
while (a >= 0 && b >= 0 && a < matrix.length && b < matrix.length) {
a = sc.nextInt();
b = sc.nextInt();
for (int i = 0; i < matrix.length; i++) {
for (int j = 0; j < matrix.length; j++) {
if (matrix[a][b].equals(asterisc)) {
matrix[i][j] = defaultValue;
} else {
matrix[a][b] = asterisc;
}
}
}
}
There are unfortunately many things wrong with your code.
Also you have not explained what your algorithm is trying to do.
In brief, to set all asterisks to defaults, you can do
for (int i = 0; i < matrix.length; i++) {
for (int j = 0; j < matrix[i].length; j++) {
if matrix[i][j].equals(asterisc){
matrix[i][j]=defaultValue;
}
}
System.out.println();
}
But
why are you using a while loop?
Why are you using a scanner?
Why are a and b initialised at zero, yet need to be greater than zero for the loop?
Are you really trying to re-initialise your whole array, every time the (a,b) item is asterisc?
I think it is not true.Suppose you have typed "6 6" in the terminal,then the variable a=6,and b=6,which is greater than the array length,and the program will throw a exception.I think the thing you may want to do can follow this codeļ¼
while(true){
a = sc.nextInt();
b = sc.nextInt();
if(a<0||a>matrix.length||b<0||b>matrix.lenght)
break;
}
Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 8 years ago.
Improve this question
Everything is good, but i just cant get the addition to show up? When I run the program it is blank when it comes to the addition of the matrixes part. Thanks in advance. BtW does anyone know how I would make this display right column justified?
public static void displayMatrixes(int[][] matrix1, int[][] matrix2, int[][] resultsMatrix) {
System.out.println("This is how i want it to output");
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
System.out.print(matrix1[i][j] + " ");
}
System.out.print("+ ");
for (int j = 0; j < 3; j++) {
System.out.print(matrix2[i][j]+ " ");
}
System.out.print("= ");
for (int j = 0; j < 3; j++) {
System.out.print(resultsMatrix[i][j]+ " ");
}
System.out.println();
}
)
This is my code
import java.util.Scanner;
public class MatrixAdd
{
public static void main(String arg[])
{
Scanner input = new Scanner(System.in);
int a[][]= new int[3][3];
int b[][] = new int[3][3];
int row, column;
System.out.println("\nEnter Matrix A: \n");
for (int i = 0 ; i < 3 ; i++){
for (int j = 0; j<3 ; j++){
a[i][j] = input.nextInt();
}
}
System.out.println("\nEnter Matrix B: \n");
for (int i = 0; i < 3; i++){
for (int j = 0; j < 3; j++){
b[i][j] = input.nextInt();
}
}
System.out.println("\nMatrix A + Matrix B = Matrix C: \n");
int[][] resultingMatrix = addMatrix(a, b);
}
public static int[][] addMatrix(int[][] a, int[][] b){
int[][] result = new int[a.length][a[0].length];
for (int i = 0; i < result.length; i++) {
for (int j = 0; j < result[0].length; j++){
result[i][j]=a[i][j] + b[i][j];
}
}
for (int i = 0; i < a.length; i++) {
char plus = '+';
for (int j = 0; j < a[0].length; j++) {
System.out.print(" " + a[i][j]);
}
if (i == a.length / 2)
System.out.print(" " + plus + " ");
else {
System.out.print(" ");
}
for (int j = 0; j < b[0].length; j++) {
System.out.print(" " + b[i][j]);
}
if (i == a.length / 2)
System.out.print(" = ");
else {
System.out.print(" ");
}
for (int j = 0; j < result[0].length; j++) {
System.out.print(" " + " " + result[i][j]);
}
System.out.println();
}
return result;
}//end of add matrices
}//end of class
I doubt that the given program compiles. In this line: int[][] resultsMatrix = displayMatrixes(a, b); you are expecting an int[][], but in your method displayMatrixes you are not returning anything. You are also expecting a 3rd parameter which you are not passing.
Also, the displayMatrixes method has no return value, which since you are returning something at the end, you must have. Try it again like so:
public static void main(String arg[]) {
Scanner input = new Scanner(System.in);
int a[][] = new int[3][3];
int b[][] = new int[3][3];
int row, column;
System.out.println("\nEnter Matrix A: \n");
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
a[i][j] = input.nextInt();
}
}
System.out.println("\nEnter Matrix B: \n");
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
b[i][j] = input.nextInt();
}
}
System.out.println("\nMatrix A + Matrix B = Matrix C: \n");
displayMatrixes(a, b);
}
public static void displayMatrixes(int[][] a, int[][] b) {
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
System.out.print(a[i][j] + " ");
}
System.out.print("+ ");
for (int j = 0; j < 3; j++) {
System.out.print(b[i][j] + " ");
}
System.out.print("= ");
for (int j = 0; j < 3; j++) {
System.out.print((a[i][j] + b[i][j]) + " ");
}
System.out.println();
}
}
}
printf with The "%3d" specifier means a minimum width of three spaces, which, by default, will be right-justified.
for your right alignment question you can at http://alvinalexander.com/programming/printf-format-cheat-sheet
Yesterday I asked a very similar question and I kind of messed up with asking it.
I need to pass an array to a method and inside of that method I need to swap the rows around so if it's
1 2 3
3 2 1
2 1 3
it needs to be
3 2 1
1 2 3
3 1 2
With the code I have right now it swaps the last column to the first column spot correctly then it puts the column that's supposed to be last.
3 1 2
1 3 2
3 2 1
Also, it needs to stay a void because I need to be modifying the original array so I can't set it as a temp array but I can use a temp integer to store.
Here is the code I have right now that's sort of working
public static void reverseRows(int[][] inTwoDArray)
{
for (int row = 0; row < inTwoDArray.length; row++)
{
for (int col = 0; col < inTwoDArray[row].length; col++)
{
int tempHolder = inTwoDArray[row][col];
inTwoDArray[row][col] = inTwoDArray[row][inTwoDArray[0].length - 1];
inTwoDArray[row][inTwoDArray[0].length - 1] = tempHolder;
}
}
}
any help would be great, I'm running out of hair to pull out! Thanks!
First, how to reverse a single 1-D array:
for(int i = 0; i < array.length / 2; i++) {
int temp = array[i];
array[i] = array[array.length - i - 1];
array[array.length - i - 1] = temp;
}
Note that you must stop in half of your array or you would swap it twice (it would be the same one you started with).
Then put it in another for loop:
for(int j = 0; j < array.length; j++){
for(int i = 0; i < array[j].length / 2; i++) {
int temp = array[j][i];
array[j][i] = array[j][array[j].length - i - 1];
array[j][array[j].length - i - 1] = temp;
}
}
Another approach would be to use some library method such as from ArrayUtils#reverse():
ArrayUtils.reverse(array);
And then again put into a cycle:
for(int i = 0; i < array.length; i++){
ArrayUtils.reverse(array[i]);
}
I guess this the easiest approach, tried and tested
For instance, you have
1 2
3 4
and you want
2 1
4 3
You can reverse the loop, without any extra space or inbuilt function.
Solution:
for(int i =0;i<arr.length;i++) //arr.length=no of rows
{
for(int j = arr[i].length-1;j>=0;j--)//arr[i].length=no of col in a ith row
{
System.out.print(arr[i][j]+" ");
}
System.out.println();
}
Not sure if I didn't confuse what array stores the rows and which one the columns.... but this should work (long time since I've done Java last, so be nice to me when spotting any errors please ^^):
public static void reverseRows(int[][] array)
{
for (int i = 0 ; i < array.length ; i++) { // for each row...
int[] reversed = new int[array[i].length]; // ... create a temporary array that will hold the reversed inner one ...
for(int j = 0 ; j < array[i].length ; j++) { // ... and for each column ...
reversed[reversed.length - 1 - j] = array[i][j]; // ... insert the current element at the mirrored position of our temporary array
}
array[i] = reversed; // finally use the reversed array as new row.
}
}
Java Code :-
import java.util.Scanner;
public class Rev_Two_D {
static int col;
static int row;
static int[][] trans_arr = new int[col][row];
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner sc = new Scanner(System.in);
int m = sc.nextInt();
row = m;
int n = sc.nextInt();
col = n;
int[][] arr = new int[row][col];
for (int i = 0; i < row; i++) {
for (int j = 0; j < col; j++) {
arr[i][j] = sc.nextInt();
System.out.print(arr[i][j] + " ");
}
System.out.println();
}
for (int j = 0; j < arr.length; j++) {
for (int i = 0; i < arr[j].length / 2; i++) {
int temp = arr[j][i];
arr[j][i] = arr[j][arr[j].length - i - 1];
arr[j][arr[j].length - i - 1] = temp;
}
}
for (int i = 0; i < row; i++) {
for (int j = 0; j < col; j++) {
System.out.print(arr[i][j] + " ");
}
System.out.println();
}
}
}
Reverse of two D array - Print your two D array in reverse order
public void reverse(){
int row = 3;
int col = 3;
int[][] arr = new int[row][col];
int k=0;
for (int i = 0; i < row; i++) {
for (int j = 0; j < col; j++,k++) {
arr[i][j] = k;
System.out.print(arr[i][j] + " ");
}
System.out.println();
}
System.out.println();
for (int i = arr.length -1; i >=0 ; i--) {
for (int j = arr.length -1; j >=0 ; j--) {
System.out.print(arr[i][j] + " ");
}
System.out.println();
}
}
public static void main(String[] args) {
int [][] a={{1,2,3,4},{5,6,7,8},{9,10,11,12},{13,14,15,16}};
for(int i=0 ; i<a.length;i++)
{
for(int j=0 ; j<a.length;j++)
{
System.out.print(a[i][j]+",");
}
System.out.println();
}
System.out.println("***************************");
for(int i=0 ; i<a.length;i++)
{
for(int j=a.length-1 ; j>=0;j--)
{
System.out.print(a[i][j]+",");
}
System.out.println();
}
}
Reverse 2 D Array
public static void main(String[] args) {
int a[][] = {{1,2,3},
{4,5,6},
{8,9,10,12,15}
};
for(int i=0 ; i<a.length;i++)
{
for(int j=0 ; j<a[i].length;j++)
{
System.out.print(a[i][j]+",");
}
System.out.println();
}
for(int i=0 ; i<a.length;i++)
{
for(int j=a[i].length-1 ; j>=0;j--)
{
System.out.print(a[i][j]+",");
}
System.out.println();
}
Assume you are given an int variable named nPositive and a 2-dimensional array of ints that has been created and assigned to a2d. Write some statements that compute the number of all the elements in the entire 2-dimensional array that are greater than zero and assign the value to nPositive.
Code:
for(int i=0; i<a2d.length; i++){
int nPositive;
for(int j=0; j<a2d[a2d.length-1].length; j++) {
if(a2d[i][j] > 0) {
nPositive = a2d[i][j];
}
}
}
It has a compilation error. Why?
The iiner cycle is incorrect:
for(int j=0; j<a2d[i].length; j++){
You didn't initialize nPositive.
// make nPositive a global variable
int nPositive = 0;
for(int i=0; i<a2d.length; i++){
for(int j=0; j<a2d[a2d.length-1].length; j++) {
if(a2d[i][j] > 0) {
nPositive += a2d[i][j]; // add the value into nPositive as you go through the array
}
}
}
I tested it and find that,There is no any compilation error in your code...
for(int j=0; j<a2d[a2d.length-1].length; j++){//
let the length is a2d[10][10]
on statement a2d[a2d.length-1].length ,is equal a2d[10-1].length ,is equal a2d[9].length=>10
your algo is working fine for me ,i found no any error
here's my test code
public class A2dTest {
public static void main(String[] arr) {
int[][] a2d = new int[10][10];
for (int i = 0; i < 10; i++) {
for (int j = 0; j < 10; j++) {
a2d[i][j] = (int) (Math.random() * 100) + 1000000;// all positives
}
}
for (int i = 0; i < a2d.length; i++) {
int nPositive = 0;
for (int j = 0; j < a2d[a2d.length - 1].length; j++) {
if (a2d[i][j] > 0) {
nPositive = a2d[i][j];
System.out.println("nPositive=" + nPositive);
}}
}
}
}
I believe this is one of the questions on codeLab. You just need to properly initialize nPositive at 0 and increment it for every positive integer. That's all they're looking for involving the output. So your code needs to be:
nPositive = 0;
for (int i = 0; i < a2d.length; i++)
{
for (int j = 0; j < a2d[i].length; j++)
{
if (a2d[i][j] > 0)
{
nPositive++;
}
}
}