I want to merge 2 Stirng arrays
the first one is merged okay but the second one keeps having null values even though it isn't empty
no errors just wrong values
what is the problem here?
public class Q4 {
public static void main(String[] args){
String array1[] = new String[]{"Ahmad", "Adam"};
String array2[] = new String[]{"Mick", "Ali"};
int n1 = array1.length;
int n2 = array2.length;
String []array3 = new String[n1+n2];
for(int i = 0; i < n1; i++)
array3[i] = array1[i];
for(int i = n1; i<n2; i++) {
int j = 0;
array3[i] = array2[j++];
}
for(int i = 0; i<array3.length; i++)
System.out.print(array3[i] + " ");
}
}
the output should be
Ahmad Adam Mick Ali
but this is what I get
Ahmad Adam null null
Your Second loop's i value is n1 size(2).and loop will continue before n2 size(2).that's why value not added.
Solution: U need add value after 1st array. If you will Store value from 1st array size ,then it will store value perfectly.
public class Q4 {
public static void main(String[] args){
String array1[] = new String[]{"Ahmad", "Adam"};
String array2[] = new String[]{"Mick", "Ali"};
int n1 = array1.length;
int n2 = array2.length;
String []array3 = new String[n1+n2];
for(int i = 0; i < n1; i++){
array3[i] = array1[i];
}
for(int i = 0; i<n2; i++) {
array3[n1++] = array2[i];
}
for(int i = 0; i<array3.length; i++)
System.out.print(array3[i] + " ");
}
}
for(int i = n1; i<n2; i++) {
the condition inside the second for loop is wrong.
As it is now you are starting from size of first array (2) to size of second array (2)
what you want should be
for(int i = n1; i<n2+n1; i++) {
also you are declaring int j inside the for loop which means j is reset each loop, move its definition outside of the loop or better yet replace it with
i-n1
In the second for loop I should've used i<array3.length instead of i<n2
since i=n1 and n2=n1 so for loop wasn't even excuted
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 was trying to create a code that rearranges given elements in an array -by the user- in ascending order, and I have done that, but the program requires
printing the given elements after sorting them firstly, then printing them before sorting.
I have no problem with printing the elements after sorting
the problem is with printing them before sorting
how to re-use ar[S] = in.nextInt() the given elements by the user out of its for loop
import java.util.*;
public class SortingnumbersANDswapping {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int swap;
int ar[] = new int[3]; //{8,10,5}
for (int S = 0; S < ar.length; S++) {
ar[S] = in.nextInt(); //this for loop is used to store numbers in the array
}
for (int i = 0; i < ar.length; i++) {
/* this nested for loop is used to compare the first element with the second one in the array
or the second element with the third.
*/
for (int j = i + 1; j < ar.length; j++) {
if (ar[i] > ar[j]) { //8>10-->F , 8>5 -->T , {5,10,8} the new arrangment we are going to use
swap = ar[i]; // 10>8-->T {5,8,10}
ar[i] = ar[j];
ar[j] = swap;
}
}
System.out.println(ar[i]); // to print the new order print it inside the array
}
// I wanna do something like that
// System.out.println(ar[S]);
// but of course I cant cause array S is only defined in it's loop
}
}
You can't reuse it, you need to keep the original array stored in another array that stays untouched. Additionally, Arrays are usually declared as int[] ar in Java, instead of int ar[]. Something along the following lines should work as intended:
public class SortingnumbersANDswapping {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int swap;
int[] ar = new int[3]; //{8,10,5}
for (int S = 0; S < ar.length; S++) {
ar[S] = in.nextInt(); //this for loop is used to store numbers in the array
}
System.out.println("::: Original Array :::");
int[] originalArray = Arrays.copyOf(ar, ar.length);
for (int j : originalArray) {
System.out.println(j);
}
System.out.println("::: Sorted Array :::");
for (int i = 0; i < ar.length; i++) {
for (int j = i + 1; j < ar.length; j++) {
if (ar[i] > ar[j]) { //8>10-->F , 8>5 -->T , {5,10,8} the new arrangment we are going to use
swap = ar[i]; // 10>8-->T {5,8,10}
ar[i] = ar[j];
ar[j] = swap;
}
}
System.out.println(ar[i]); // to print the new order print it inside the array
}
}
}
You can do a copy of the array using the copyOf method from the Arrays library (java.util.Arrays) before you start changing the array.
Here you can find some different approaches - https://www.softwaretestinghelp.com/java-copy-array/amp/
You can use System.out.print(Arrays.toString(arr)); to print the entire array.
public static void main(String... args) {
int[] arr = readArray(3);
System.out.print(Arrays.toString(arr));
for (int i = 0; i < arr.length; i++) {
for (int j = i + 1; j < ar.length; j++) {
if (arr[i] > arr[j]) {
swap(arr, i, j);
System.out.print(Arrays.toString(arr));
}
}
}
}
private static int[] readArray(int size) {
System.out.format("Enter %d elements:\n", size);
Scanner scan = new Scanner(System.in);
int[] arr = new int[size];
for(itn i = 0; i < arr.length; i++)
arr[i] = scan.nextInt();
return arr;
}
private static void swap(int[] arr, int i, int j) {
int tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
Hey guys I want to write program that shifts elements in an array once to the left but I tried everything and it's not working. The code below is outputting just 0's. Can someone please tell me how I can do this. Thank you!
import java.util.Scanner;
public class StudentScores {
public static void main (String [] args) {
Scanner scnr = new Scanner(System.in);
final int SCORES_SIZE = 4;
int[] oldScores = new int[SCORES_SIZE];
int[] newScores = new int[SCORES_SIZE];
int i;
for (i = 0; i < oldScores.length; ++i) {
oldScores[i] = scnr.nextInt();
}
int temp = newScores[0];
for (i = 0; i < oldScores.length - 1; ++i) {
newScores[i] = newScores[i+1];
}
temp = newScores[oldScores.length - 1];
for (i = 0; i < newScores.length; ++i) {
System.out.print(newScores[i] + " ");
}
System.out.println();
}
}````
As pointed out by people in comments, you seem to be assigning newScores[] to newScores[] value(an uninitialized array has all values set to 0):
int temp = newScores[0]; // Should be oldScores[0]
// ...
newScores[i] = newScores[i+1]; // Should be oldScores[i+1]
You need to have oldScores[] values on RHS. Since you only want to shift by one place, I think extra array is unnecessary. You can do it in place like this:
int temp = oldScores[0];
for (i = 0; i < oldScores.length - 1; ++i) {
oldScores[i] = oldScores[i + 1];
}
oldScores[oldScores.length - 1] = temp;
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]);
}
}
}