I have an array (Arr). I fill points1 and points2 with values.
public class Arr {
float pointX;
float pointY;
boolean yesNo;
String text;
}
public Arr points1[];
public Arr points2[];
points1 = new Arr[100];
for (int i = 0; i < 100; i++) points1[i]= new Arr();
for (int j = 0; j < 100; j++) {
points1[j].pointX = getFloat;
points1[j].pointY = getFloat;
points1[j].yesNo = getBoolean;
points1[j].text = getText;
}
points2 = new Arr[100];
for (int x = 0; x < 100; x++) points2[x]= new Arr();
for (int y = 0; y < 100; y++) {
points2[y].pointX = getFloat;
points2[y].pointY = getFloat;
points2[y].yesNo = getBoolean;
points2[y].text = getText;
}
This works, but what is, when I have five of them or more (points1, points2, points3...)
How can I make "public Arr points[][]"? And then fill and get the values with e.g. points[0][22].pointX or points[1][10].text?
And how can I see the points[][] array like var_dump in PHP? How list the array?
var_dump example:
array(3) {
[0]=>
int(1)
[1]=>
int(2)
[2]=>
array(3) {
[0]=>
string(1) "a"
[1]=>
string(1) "b"
[2]=>
string(1) "c"
}
}
This is a working example
package com.stackoverflow.q15134193;
public class Test1 {
public static Arr[][] points;
static float getFloat = 1;
static boolean getBoolean = true;
static String getText = "hi";
public static void main(String[] args) {
points = new Arr[100][];
for (int i = 0; i < points.length; i++) {
points[i] = new Arr[100];
for (int j = 0; j < points[i].length; j++)
points[i][j] = new Arr();
}
for (int i = 0; i < points.length; i++) {
for (int j = 0; j < points[i].length; j++) {
points[i][j].pointX = getFloat;
points[i][j].pointY = getFloat;
points[i][j].yesNo = getBoolean;
points[i][j].text = getText;
}
}
for (int i = 0; i < points.length; i++)
for (int j = 0; j < points[i].length; j++)
System.out.println("X: " + points[i][j].pointX + " Y: "
+ points[i][j].pointY + " YesNo: "
+ points[i][j].yesNo
+ " text: "+ points[i][j].text);
}
}
class Arr {
public float pointX;
public float pointY;
public boolean yesNo;
public String text;
}
I'm not completely clear on what you're trying to achieve, but Java isn't PHP.
Java has an extensive set of Collections which will give you much better coverage then simple array's.
As I'm not completely sure what you're trying to do, I can't really tell you what collections could do the job, but you could read up on things like Maps and ArrayList.
You could make, per example an ArrayList of 'Arr's like
ArrayList<Arr> list = new ArrayList<Arr>();
Similarly you can do ArrayList<Arr, Arr>, or start working with Maps if you want to store your object Arr together with a key to find it with.
Once you're using a Java Collection, the clearest way to print these is just looping over it , with something like
for(Arr a : list){
Log.d("my_tag", "My list contains"+a.toString());
}
Instead of 2D array, you can use ArrayList.
ArrayList<Arr> points = new ArrayList<Arr>();
Now, access an index as following:
points.get(22).pointX OR points.get(10).text
Try to print the arraylist points, to see a near about string output:
System.out.println(points);
You need to implement a toString() method in your class Arr, and then call
Log.i("mytag", Arrays.toString(points1));
as explained here how see an array in logcat for android
Related
Im trying to initialise all the elements of the 2d array into a string "EMPTY". but When ever I try to initialise the array it gets null values. I checked errors in the for loop but couldn't see any
public static void arr_2d(){
String [][] arr = new String[3][2];
for (int i = 0; i < arr.length; i++) {
for (int a = 0; a < arr[i].length; a++) {
arr[i][a] = "EMPTY";
}
for (int b = 0; b < arr.length; b++) {
for (int j = 0; j < arr[b].length; j++) {
System.out.print(arr[b][j] + " ");
}
System.out.println();
}
}
}
Your loops are nested wrongly, which will result in the filling process not being complete while you're trying to process its results. You need
public static void arr_2d() {
String[][] arr = new String[3][2];
for (int i = 0; i < arr.length; i++) {
for (int a = 0; a < arr[i].length; a++) {
arr[i][a] = "EMPTY";
}
}
for (int b = 0; b < arr.length; b++) {
for (int j = 0; j < arr[b].length; j++) {
System.out.print(arr[b][j] + " ");
}
System.out.println();
}
}
Actually for(int b) is in for(int i); that's why you observe null values. If you move for(int b) outside of for(int i), there will be no null values.
public static void arr_2d(){
String [][] arr = new String[3][2];
for (int i = 0; i < arr.length; i++) {
for (int a = 0; a < arr[i].length; a++) {
arr[i][a] = "EMPTY";
}
}
for (int b = 0; b < arr.length; b++) {
for (int j = 0; j < arr[b].length; j++) {
System.out.print(arr[b][j] + " ");
}
System.out.println();
}
}
Check the comments given below in the snippet:
public static void arr_2d(){
String [][] arr = new String[3][2];
for (int i = 0; i < arr.length; i++) {
for (int a = 0; a < arr[i].length; a++) {
arr[i][a] = "EMPTY";
// you can have the sysout statement here as well instead of having looping the entire array again.
System.out.print(arr[i][a] + " ");
}
// this loop must be executed separately inorder to check values present in the array or else you can have a sysout statement when assigning the "empty" value in the array.
for (int b = 0; b < arr.length; b++) {
for (int j = 0; j < arr[b].length; j++) {
System.out.print(arr[b][j] + " ");
}
System.out.println();
}
}
}
Although the answers you have are correct I will add that one problem is your code style is prone to errors.
Your mistake was traversing the array incorrectly. The correct way is traversing the array twice, one of filling and another for printing, but instead it seems you have attempted to do everything in one shot. That mistake can be avoided with a better code style.
This is how I would have written your code in imperative style:
String[][] arr = new String[3][2];
for (String[] a : arr)
Arrays.fill(a, "EMPTY");
for (String[] a : arr)
System.out.println(Arrays.toString(a));
Notice the code is much shorter, so there's less chances of mistakes. It's also a lot more obvious that you're traversing twice.
Instead of traversing an array explicitly:
for (int i = 0; i++; i < arr.length())
Use the implicit for loop:
for (String[] value: arr)
Instead of filling an array explicitly:
for (int a = 0; a < arr[i].length; a++) {
arr[i][a] = "EMPTY";
}
Use the already provided fill method:
Arrays.fill(value, "EMPTY");
Instead of printing an array explicitly:
for (String string : strings) {
System.out.print(string + " ");
}
System.out.println();
Use the already provided print method:
for (String[] a : arr)
System.out.println(Arrays.toString(a));
However, I would have written in functional style:
String [][] arr = new String[3][2];
Arrays.stream(arr)
.forEach(a -> Arrays.fill(a, "EMPTY"));
Arrays.stream(arr)
.map(Arrays::toString)
.forEach(System.out::println);
One particular advantage is that you are encouraged to think in a more abstract way. Instead of thinking how to explicitly set or print each element of the array, you are encouraged to use methods that implicitly traverse, transform or perform generic computations on all elements of the array.
I have to define a method called getDistance. That takes the following string:
0,900,1500<>900,0,1250<>1500,1250,0 and returns a 2d array with the all the distances. The distances are separated by "<>" symbol and they are separated into each column by ",".
I know I need to use String.split method. I know splitting by the commmas will give me the columns and splitting it by the "<>" will give me the rows.
public static int[][] getDistance(String array) {
String[]row= array.split(",");
String[][] distance;
int[][] ctyCoord = new int[3][3];
for (int k = 0; k < row.length; k++) {
distance[k][]=row[k].split("<>");
ctyCoord[k][j] = Integer.parseInt(str[j]);
}
return ctyCoord;
This is a working dynamic solution:
public static int[][] getDistance(String array) {
String[] rows = array.split("<>");
int[][] _2d = null;
// let us take the column size now, because we already got the row size
if (rows.length > 0) {
String[] cols = rows[0].split(",");
_2d = new int[rows.length][cols.length];
}
for (int i = 0; i < rows.length; i++) {
String[] cols = rows[i].split(",");
for (int j = 0; j < cols.length; j++) {
_2d[i][j] = Integer.parseInt(cols[j]);
}
}
return _2d;
}
Let's test it:
public static void main(String[] args) {
String given = "0,900,1500<>900,0,1250<>1500,1250,0";
int[][] ok = getDistance(given);
for (int i = 0; i < ok.length; i++) {
for (int j = 0; j < ok[0].length; j++) {
int k = ok[i][j];
System.out.print(k + " ");
}
System.out.println();
}
}
I think you should first split along the rows and then the colums. I would also scale the outer array with the number of distances.
public static int[][] getDistance(String array) {
String[] rows = array.split("<>");
int[][] out = new int[rows.length][3];
for (int i = 0; i < rows.length, i++) {
String values = rows[i].split(",");
for (int j = 0; j < 3, j++) {
out[i][j] = Integer.valueOf(values[j]);
}
}
return out;
I want to swap Columns and Rows in a 2D array.
My problem is that I want the Variable "oldField" to save the oldField. The Variable I think is Pointing on the same Object as newField and so it get´s changed even tho I dont want that.
Id like to know how I can save the Variable oldField independent
public int[][] swapMatrix(int[][] pField) { // swaps the rows and columns in
// a Field
int[][] oldField = pField.clone();
int[][] newField = pField.clone();
for (int i = 0; i < newField.length; i++) {
for (int j = (newField.length - 1); j >= 0; j--) {
newField[i][(newField.length - 1) - j] = oldField[j][i];
}
}
return newField;
}
When you copy in 1-D array with primitive value like int then the new array and content copy to it and there is no reference.
int row1[] = {0,1,2,3};
int row2[] = row1.clone();
row2[0] = 10;
System.out.println(row1[0] == row2[0]); // prints false
but for 2-D array the content is object and clone method only do shallow copy not create new content if object is there .For your requirement you need to do deep copy.
int table1[][]={{0,1,2,3},{11,12,13,14}};
int table2[][] = table1.clone();
table2[0][0] = 100;
System.out.println(table1[0][0] == table2[0][0]); //prints true
this code solves your problem:
public class SwapRowsAndColumns {
public static void main(String[] args) {
int[][] someMatrix = new int[2][3];
someMatrix[0][0] = 1;
someMatrix[0][1] = 2;
someMatrix[0][2] = 3;
someMatrix[1][0] = 4;
someMatrix[1][1] = 5;
someMatrix[1][2] = 6;
printMatrix(someMatrix);
int[][] invertedMatrix = swapMatrix(someMatrix);
printMatrix(invertedMatrix);
}
private static int[][] swapMatrix(int[][] pField) {
int originalTotalRows = pField.length;
int originalTotalColumns = pField[0].length;
int[][] newMatrix = new int[originalTotalColumns][originalTotalRows];
for(int i=0; i< originalTotalRows; i++){
for(int j=0; j < originalTotalColumns; j++){
newMatrix[j][i] = pField[i][j];
}
}
return newMatrix;
}
private static void printMatrix(int[][] matrix){
int totalRows = matrix.length;
int totalColumns = matrix[0].length;
for(int i=0; i< totalRows; i++){
for(int j=0; j< totalColumns; j++){
System.out.print(matrix[i][j] + " ");
}
System.out.println("");
}
}
}
I'm trying to populate a 2D array with char's from a string I've read in. I'm having a problem with actually populating this 2D array. It keeps printing a 2D array bigger than what I've given it, and the number always seems to be 6 rather than the letters from the string.
I store the string in an ArrayList called tempArray.
Input strings:
WUBDLAIUWBD
LUBELUFBSLI
SLUEFLISUEB
I instantiate a 2D array with columnlength = 11, and rowcount 3
epidemicArray = new int[rowCount][columnCount];
Array before I try to populate it:
00000000000
00000000000
00000000000
My code:
public static void updateArray(){
//extract string from temp
for (int i = 0; i < tempArray.size(); i++){
String temp = tempArray.get(i);
char[] charz = temp.toCharArray();
for (int j = 0; j < charz.length; j++){
for (int k = 0; k < rowCount; k++){
for (int l = 0; l < columnCount; l++){
epidemicArray[k][l] = charz[j];
}
}
}
}
}
Output: Which I didn't expect
6666666666666666666666
6666666666666666666666
6666666666666666666666
Expected output: (2D array)
WUBDLAIUWBD
LUBELUFBSLI
SLUEFLISUEB
Thanks, this is really bugging me.
Change your code to this:
public static void updateArray(){
//extract string from temp
for (int i = 0; i < tempArray.size(); i++){
String temp = tempArray.get(i);
char[] charz = temp.toCharArray();
for (int j = 0; j < charz.length; j++){
epidemicArray[i][j] = charz[j];
}
}
}
This edit should work since the number of columns is the length of one of the string (same length for the 3 of them).
Here is my output
[EDIT]. #magna_nz, I used the following methods to print the array
public static void printRow(int rowNumber) {
for (int i = 0; i < 11; i++) {
System.out.print( epidemicArray[rowNumber][i] + " ");
}
System.out.println();
}
public static void main(String[] args) {
updateArray();
for (int i = 0; i < 3; i++) {
printRow(i);
}
}
This will print the numbers, but if you want to print characters you can change the above printRow method to something like:
public static void printRow(int rowNumber) {
for (int i = 0; i < 11; i++) {
System.out.print( (char)epidemicArray[rowNumber][i] + " ");
}
System.out.println();
}
And this will give you the following result:
You're overwriting your entire epidemicArray with the last value that charz[j] gets. Which is apparently 66. Actually you're overwriting that entire array with every value from charz and the last one won.
I have problem with conversion from String into two dimension int array.
Let's say I have:
String x = "1,2,3;4,5,6;7,8,9"
(In my program it will be String from text area.) and I want to create array n x n
int[3][3] y = {{1,2,3},{4,5,6},{7,8,9}}
(Necessary for next stages.) I try to split the string and create 1 dimensional array, but I don't have any good idea what to do next.
As you suggest I try split at first using ; then , but my solution isn’t great. It works only when there will be 3 x 3 table. How to create a loop making String arrays?
public int[][] RunMSTFromTextFile(JTextArea ta)
{
String p = ta.getText();
String[] tp = p.split(";");
String tpA[] = tp[0].split(",");
String tpB[] = tp[1].split(",");
String tpC[] = tp[2].split(",");
String tpD[][] = {tpA, tpB, tpC};
int matrix[][] = new int[tpD.length][tpD.length];
for(int i=0;i<tpD.length;i++)
{
for(int j=0;j<tpD.length;j++)
{
matrix[i][j] = Integer.parseInt(tpD[i][j]);
}
}
return matrix;
}
After using split, take a look at Integer.parseInt() to get the numbers out.
String lines[] = input.split(";");
int width = lines.length;
String cells[] = lines[0].split(",");
int height = cells.length;
int output[][] = new int[width][height];
for (int i=0; i<width; i++) {
String cells[] = lines[i].split(",");
for(int j=0; j<height; j++) {
output[i][j] = Integer.parseInt(cells[j]);
}
}
Then you need to decide what to do with NumberFormatExceptions
Split by ; to get rows.
Loop them, incrementing a counter (e.g. x)
Split by , to get values of each row.
Loop those values, incrementing a counter (e.g. y)
Parse each value (e.g. using one of the parseInt methods of Integer) and add it to the x,y of the array.
If you have already created an int[9] and want to split it into int[3][3]:
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
toArray[i][j] = fromArray[(3*i) + j);
}
}
Now, if the 2-dimensional array is not rectangular, i.e. the size of inner array is not same for all outer arrays, then you need more work. You would do best to use a Scanner and switch between nextString and next. The biggest challenge will be that you will not know the number of elements (columns) in each row until you reach the row-terminating semi-colon
A solution using 2 splits:
String input = "1,2,3;4,5,6;7,8,9";
String[] x = input.split(";");
String[][] result = new String[x.length][];
for (int i = 0; i<x.length; i++) {
result[i] = x[i].split(",");
}
This give a 2 dimension array of strings you will need to parse those ints afterwards, it depends on the use you want for those numbers. The following solution shows how to parse them as you build the result:
String input = "1,2,3;4,5,6;7,8,9";
String[] x = input.split(";");
int[][] result = new int[x.length][];
for (int i = 0; i < x.length; i++) {
String[] row = x[i].split(",");
result[i] = new int[row.length];
for(int j=0; j < row.length; j++) {
result[i][j] = Integer.parseInt(row[j]);
}
}
Super simple method!!!
package ADVANCED;
import java.util.Arrays;
import java.util.Scanner;
public class p9 {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner sc=new Scanner(System.in);
String x=sc.nextLine();
String[] array = x.split(",");
int length_x=array.length;
int[][] two=new int[length_x/2][2];
for (int i = 0; i <= length_x-1; i=i+2) {
two[i/2][0] = Integer.parseInt(array[i]);
}
for (int i = 1; i <= length_x-1; i=i+2) {
two[i/2][1] = Integer.parseInt(array[i]);
}
}
}