Develop Reference

Problems with iterated nextLine function

I am trying to use user inputted N lines of N characters to do some operations with. But first I need to know N and another int being inputted. When I define N and the other integer K and then write 5 lines (in this case) of 5 characters each the program runs well. But when I use the represented String a (which I then would split into 2 ints, N and K, not shown here to not complicate things), an error occurs. Even if I now input 6 lines, being the 5 last of 5 characters each, the program gives an error of no line found for the multi function. I don't understand what's the problem, and if I remove the string a and just define N and K the program runs well. What's more surprising, the program runs if I use an interactive console instead of text input and write the terms one by one.
static String [][] vetor (int N) {
Scanner scan = new Scanner(System.in);
String[][] multi = new String [N][N];
for (int i = 0 ; i<N ; i++){
String forest = scan.nextLine();
String[] chars = forest.split("");
for (int k=0; k<N; k++){
multi[i][k]= chars [k];
}
}
return multi;
}
public static void main(String args[]) {
Scanner scan = new Scanner(System.in);
String a = scan.nextLine();
int N = 5;
int K = 5;
String [][] multi = vetor(N);
I've tried many things, but I can't make sense of this. I didn't find any similar questions, but feel free to redirect me to an explanation.
Edit: This is a similar program one can run (with a possible input down (K<= N)) :
import java.util.Scanner;
import java.util.Arrays;
public class Main {
static int[] numerificar() {
Scanner myObj = new Scanner(System.in);
String Input = myObj.nextLine();
String[] Inputs = Input.split(" ", 0);
int size = Inputs.length;
int [] a = new int [size];
for(int i=0; i<size; i++) {
a[i] = Integer.parseInt(Inputs[i]);}
return a;
}
static String [][] vetor (int N) {
Scanner scan = new Scanner(System.in);
String[][] multi = new String [N][N];
for (int i = 0 ; i<N ; i++){
String forest = scan.nextLine();
String[] chars = forest.split("");
for (int k=0; k<N; k++){
multi[i][k]= chars [k];
}
}
return multi;
}
public static void main(String args[]) {
Scanner scan = new Scanner(System.in);
int[] a = numerificar();
int N = a[0];
int K = a[1];
int cadeira = 0;
String [][] multi = vetor(N);
for (int i = 0 ; i<N ; i++){
if (cadeira == 1) {
break;
}
for (int k=0; k<N-K+1; k++){
if (cadeira == 1) {
break;
}else if( multi[i][k].equals(".")){
for (int j=0; j<K; j++){
if(multi[i][k+j].equals( "#")){
k+=j;
break;
} else if (j == K-1) {
cadeira = 1;
}
}
}
}
}
System.out.println(cadeira);
}
}
5 3
.#.##
#####
##...
###..
#####
The output should be 1 in this case.

The problem is you are creating more than one Scanner that reads from System.in. When data is readily available, a Scanner object can read more data than you ask from it. The first Scanner, in the numerificar() method, reads more than the first line, and those lines are not available to the second Scanner, in the vetor() method.
Solution: use just one Scanner object in the whole program.
public class Main {
static Scanner globalScanner = new Scanner(System.in);
static int[] numerificar() {
String Input = globalScanner.nextLine();
String[] Inputs = Input.split(" ", 0);

Why does my method that I am trying to call to inside main not work?

minGap(array); is not being recognized. I don't know what I have done wrong, but I am sure it is a super simple fix. Trying to figure out if it is something to do with the data type being used or if it has something to do with the arrangement of the line " " added. Any hints?
package Lab8;
import java.util.*;
import java.util.Scanner;
public class Question_One {
public static void main(String args[]) {
int length;
Scanner input = new Scanner(System.in); //scanner to input any size array user wants
System.out.println("Please enter the numbers for the array.");
length = input.nextInt();
String[] array = new String[length];
for(int i = 0;i <length;i++) { //counter logic
System.out.println("How many integers are in the array?"+(i+1));
array[i] = input.nextLine();
}
System.out.println("Enter the numbers for the array (individually):");
for(int i = 0;i <length;i++) { //counter logic
System.out.print(array [i]);
array[i] = input.nextLine();
}
input.close();
minGap(array);
}
private static int minGap(int a[], int gapMin) {
int []gap = new int[a.length];
//a
for (int i=0;i<a.length-2;i++) {
if (gapMin>gap[i]) {
gapMin=gap[1];
}
}
return gapMin;
}
}

I believe you wanted a method to find the minimum gap. As such, you should not be passing that into the method. Your logic is also a bit off, you want to take the minimum value after gapMin>gap[i] (not a hardcoded gap[1]). So you could do,
private static int minGap(int a[]) {
int gapMin = Integer.MAX_VALUE;
int[] gap = new int[a.length];
for (int i = 0; i < a.length; i++) {
if (gapMin > gap[i]) {
gapMin = gap[i];
}
}
return gapMin;
}
or (if you're using Java 8+)
private static int minGap(int a[]) {
return Arrays.stream(a).min().getAsInt();
}
Then you need to actually save that value or print it. That is, change
minGap(array);
to (just print it)
System.out.println(minGap(array));
And you need an array of int (not a String[]).
int[] array = new int[length];
for(int i = 0; i < length; i++) {
System.out.printf("Please enter integer %d for the array%n", i + 1);
array[i] = input.nextInt();
}

How to convert a char array to an int array?

Say I am using this code to convert a String (containing numbers) to an array of characters, which I want to convert to an array of numbers (int).
(Then I want to do this for another string of numbers, and add the two int arrays to give another int array of their addition.)
What should I do?
import java.util.Scanner;
public class stringHundredDigitArray {
/**
* #param args
*/
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.print("Enter the number: ");
String num1 = in.nextLine();
char[] num1CharArray = num1.toCharArray();
//for (int i = 0; i < num1CharArray.length; i++){
//System.out.print(" "+num1CharArray[i]);
//}
int[] num1intarray = new int[num1CharArray.length];
for (int i = 0; i < num1CharArray.length; i++){
num1intarray[i] = num1CharArray[i];
}
for (int i = 0; i < num1intarray.length; i++){ //this code prints presumably the ascii values of the number characters, not the numbers themselves. This is the problem.
System.out.print(" "+num1intarray[i]);
}
}
}
I really have to split the string, to preferably an array of additionable data types.

try Character.getNumericValue(char); this:
for (int i = 0; i < num1CharArray.length; i++){
num1intarray[i] = Character.getNumericValue(num1CharArray[i]);
}

Try This :
int[] num1intarray = new int[num1CharArray.length];
for (int i = 0; i < num1CharArray.length; i++)
{
num1intarray[i]=Integer.parseInt(""+num1CharArray[i]);
System.out.print(num1intarray[i]);
}

Short and simple solution!
int[] result = new int[charArray.length];
Arrays.setAll(result, i -> Character.getNumericValue(charArray[i]));

How to get a certain array element's key?

I'm pretty new to java, and I'm trying to create a simple method that sorts inputted numbers, either ascending or descending. However, there's a problem that I can't put in repeated values. Is there a way to get the key of a certain item of an array??
My code:
import java.io.Console;
public class TestSort {
public static void main(String args[]) {
Console c = System.console();
if (c == null) {
System.err.println("No console.");
System.exit(1);
}
System.out.println("TESTSORT.java");
System.out.println("-------------");
System.out.println("Type in a set of numbers here:");
String in = c.readLine();
System.out.println("(A)scending or (D)escending");
String ad = c.readLine();
boolean d = false;
if(ad.equals("a")) d = false;
else if(ad.equals("d")) d = true;
else {
System.out.println("Invalid Input.");
System.exit(1);
}
String[] in2 = in.split(" ");
int[] x = new int[in2.length];
int count1 = 0;
for(String val : in2)
x[count1++] = Integer.parseInt(val);
int[] a = new int[x.length];
int count = 0;
for(int y : x) {
for(int z : x) {
// if index of y equals index of z continue
if(z < y) count++;
}
a[count] = y;
count = 0;
}
if(d) {
int[] arr3 = new int[a.length];
int length = a.length;
for(int b : a) arr3[--length] = b;
for(int b : arr3) System.out.println(b);
} else
for(int b : a)
System.out.println(b);
}
}
This program just counts up the number of other numbers smaller than itself, but not including itself. However, it doesn't differentiate itself from other numbers with the same value.
Help would be appreciated.
Thanks.

To get the index of a certain value for an array you will have to loop through the array. However if there is multiple entries with the same value this approach wouldn't work (without modification)
int indexVal = -1;
int inputValue; // This is your input vlaue you are trying to find
for(int i = 0; i < array.length ; i++)
{
if (array[i] == inputValue)
{
indexVal = i;
break;
}
}
You may also want to look at Array.sort for built in array sorrting

If you want an index you should not be using for each loops. You will have to use a regular for loop to get at an index in the array.

A SortedSet is perfect for this. As a set, it does not allow duplicate values, and it is sorted automatically for you!
Just add your elements to the set, e.g:
SortedSet<Integer> set = new SortedSet<Integer>();
for(String value : in2.split(" ")){
set.add(Integer.parseInt(value));
}
To reverse the order of the set do something like this:
SortedSet<Integer> descending = set.descendingSet();
You can iterate through sets just like arrays too:
for(Integer i : set){
//Do something
}
Good luck!

Reading 2-D array from a file

I have a 2-D int array in file 'array.txt'. I am trying to read all the elements in the file in a two dimensional array. I am having problem in copying. It shows all the elements having value '0' after copying instead their original value. Please help me.
My code is :
import java.util.*;
import java.lang.*;
import java.io.*;
public class appMainNineSix {
/**
* #param args
*/
public static void main(String[] args)
throws java.io.FileNotFoundException{
// TODO Auto-generated method stub
Scanner input = new Scanner (new File("src/array.txt"));
int m = 3;
int n = 5;
int[][] a = new int [m][n];
while (input.next()!=null){
for (int i=0;i<m;i++){
for (int j=0;j<n;j++)
a[i][j]= input.nextInt();
}
}
//print the input matrix
System.out.println("The input sorted matrix is : ");
for(int i=0;i<m;i++){
for(int j=0;j<n;j++)
System.out.println(a[i][j]);
}
}
}

while (input.next()!=null)
This will consume something from the scanner input stream. Instead, try using while (input.hasNextInt())
Depending on how robust you want your code to be, you should also check inside the for loop that something is available to be read.
Scanner input = new Scanner (new File("src/array.txt"));
// pre-read in the number of rows/columns
int rows = 0;
int columns = 0;
while(input.hasNextLine())
{
++rows;
Scanner colReader = new Scanner(input.nextLine());
while(colReader.hasNextInt())
{
++columns;
}
}
int[][] a = new int[rows][columns];
input.close();
// read in the data
input = new Scanner(new File("src/array.txt"));
for(int i = 0; i &lt rows; ++i)
{
for(int j = 0; j &lt columns; ++j)
{
if(input.hasNextInt())
{
a[i][j] = input.nextInt();
}
}
}
An alternative using ArrayLists (no pre-reading required):
// read in the data
ArrayList&ltArrayList&ltInteger&gt&gt a = new ArrayList&ltArrayList&ltInteger&gt&gt();
Scanner input = new Scanner(new File("src/array.txt"));
while(input.hasNextLine())
{
Scanner colReader = new Scanner(input.nextLine());
ArrayList col = new ArrayList();
while(colReader.hasNextInt())
{
col.add(colReader.nextInt());
}
a.add(col);
}

The problem is when u reach the end of the file it throughs an exception that no usch element exist.
public static void main(String[] args) {
// TODO Auto-generated method stub
try {
Scanner input = new Scanner(new File("array.txt"));
int m = 3;
int n = 5;
int[][] a = new int[m][n];
while (input.hasNextLine()) {
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
try{// System.out.println("number is ");
a[i][j] = input.nextInt();
System.out.println("number is "+ a[i][j]);
}
catch (java.util.NoSuchElementException e) {
// e.printStackTrace();
}
}
} //print the input matrix
System.out.println("The input sorted matrix is : ");
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
System.out.println(a[i][j]);
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
I knew that making catch without processing the exception but it temporary works.
Please be aware I put the file outside the source folder.

Well the problem may be that you've got that pair of nested loops to read the numbers stuck inside that while loop. Why would you want to re-read the array values after you've read them once? And note that if there's anything in the file after the last number, then you'll fill the array in with whatever .nextInt() returns after end-of-file has been reached!
edit — well .nextInt() should throw an exception I guess when input runs out, so that may not be the problem.

Start simple...
change:
for (int j=0;j<n;j++)
a[i][j]= input.nextInt();
to:
for (int j=0;j<n;j++)
{
int value;
value = input.nextInt();
a[i][j] = value;
System.out.println("value[" + i + "][" + j + " = " + value);
}
And make sure that the values are read in.
Also, you should not call next without first calling (and checking) hasNext (or nextInt/hasNextInt).

You can try Using Guava ,
public class MatrixFile {
private final int[][] matrix;
public MatrixFile(String filepath) {
// since we don't know how many rows there is going to be, we will
// create a list to hold dynamic arrays instead
List<int[]> dynamicMatrix = Lists.newArrayList();
try {
// use Guava to read file from resources folder
String content = Resources.toString(
Resources.getResource(filepath),
Charsets.UTF_8
);
Arrays.stream(content.split("\n"))
.forEach(line -> {
dynamicMatrix.add(
Arrays.stream(line.split(" "))
.mapToInt(Integer::parseInt)
.toArray()
);
});
} catch (IOException e) {
// in case of error, always log error!
System.err.println("MatrixFile has trouble reading file");
e.printStackTrace();
}
matrix = dynamicMatrix.stream().toArray(int[][]::new);
}