I got a little problem here with Java and I am fairly new to it.
My program reads a String via InputStreamReader and saves it in the String input.
How do I save the elements of the String in a 2d char array with n x m elements?
Edit:
I think I´ve got a solution:
I used 2 for-loops (is that the right english translation for it? ) and .toCharArray to convert the String.
public static char[][] transform (String text, int arrBreite, int arrLaenge) {
char[][] returnArray = new char[arrBreite][arrLaenge];
char[] buffer = text.toCharArray();
for (int i = 0; i < arrBreite; i++) {
for (int j = 0; j <arrLaenge; j++) {
if (((i * arrBreite) + j) > buffer.length - 1) returnArray[i][j] = " ".charAt(0);
else returnArray[i][j] = buffer[(i*arrBreite)+j];
}
}
return returnArray;
}
Thanks for your help guys.
You can use the toCharArray() method to get a char array from your String.
If you need to split with a given delimiter to determine the array lines, you use first the Split method on the String, then use toCharArray to create your 2 dimensional array.
You should use String.toCharArray().
Related
I have been given a homework assignment as follows:
Read three sentences from the console application. Each sentence should not exceed 80 characters. Then, copy each character in each input sentence in a [3 x 80] character array.
The first sentence should be loaded into the first row in the reverse order of characters – for example, “mary had a little lamb” should be loaded into the array as “bmal elttil a dah yram”.
The second sentence should be loaded into the second row in the reverse order of words – for example, “mary had a little lamb” should be loaded into the array as “lamb little a had mary”.
The third sentence should be loaded into the third row where if the index of the array is divisible by 5, then the corresponding character is replaced by the letter ‘z’ – for example, “mary had a little lamb” should be loaded into the array as “mary zad azlittze lazb” – that is, characters in index
positions 5, 10, 15, and 20 were replaced by ‘z’. Note that an empty space is also a character, and that the index starts from position 0.
Now print the contents of the character array on the console.
The methods, return types, and parameters in the code below are all specified as required so I cannot change any of that information. I am having trouble initializing the 2d array. The instructions say that the sentences must be loaded into the array already reversed etc. but the parameters of the methods for doing this calls for strings. I assume that means I should read the lines as strings and then call the methods to modify them, then use toCharyArray to convert them before loading them into the 2d array. I don't understand how to initialize the 2D array with the values of the char arrays. Is there some kind of for loop I can use? Another issue is that no processing can be done inside of the main method but in the instructions there is no method that I can call to fill the array.
import java.util.regex.Pattern;
public class ReversedSentence {
public static String change5thPosition(String s){
char[] chars = s.toCharArray();
for (int i = 5; i < s.length(); i = i + 5) {
chars[i] = 'z';
}
String newString = new String(chars);
return newString;
}
public static String printChar2DArray(char[][] arr){
for (int x = 0; x < 3; x++) {
for (int y = 0; y < 80; y++) {
// just a print so it does not make new lines for every char
System.out.print(arr[x][y]);
}
}
return null;
}
public static String reverseByCharacter(String s){
String reverse = new StringBuffer(s).reverse().toString();
return reverse;
}
public static String reverseByWord(String s){
Pattern pattern = Pattern.compile("\\s"); //splitting the string whenever there
String[] temp = pattern.split(s); // is whitespace and store in temp array.
String result = "";
for (int i = 0; i < temp.length; i++) {
if (i == temp.length - 1)
result = temp[i] + result;
else
result = " " + temp[i] + result;
}
return result;
}
public static String truncateSentence(String s){
if (s==null || s.length() <= 80)
return s;
int space = s.lastIndexOf(' ', 80);
if (space < 0)
return s.substring(0, 80);
return s;
}
public static void main(String[] args) {
String sentence1 = ("No one was available, so I went to the movies alone.");
String sentence2 = "Ever since I started working out, I am so tired.";
String sentence3 = "I have two dogs and they are both equally cute.";
char[][] arr = new char[3][80];
arr[0] = reverseByCharacter(sentence1).toCharArray();
arr[1] = reverseByWord(sentence2).toCharArray();
arr[2] = change5thPosition(sentence3).toCharArray();
printChar2DArray(arr);
}
}
The error I am getting is:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 52 out of bounds for length 52
at ReversedSentence.printChar2DArray(ReversedSentence.java:20)
at ReversedSentence.main(ReversedSentence.java:71)
.enola seivom eht ot tnew I os ,elbaliava saw eno oN
The problem is that in your printChar2DArray method you assume that every array has the length of 80, but that's actually not the case here. In Java, a 2D array is just an array of arrays. So, when you have this: char[][] arr = new char[3][80], you are creating an array of 3 arrays, and each of these arrays has the length of 80 characters. That may seem ok, but in the next lines you reinitialize the 3 arrays with something different entirely.
arr[0] = reverseByCharacter(sentence1).toCharArray();
arr[1] = reverseByWord(sentence2).toCharArray();
arr[2] = change5thPosition(sentence3).toCharArray();
Now none of these arrays has the length of 80. Each of them has the length of the respective string.
You can solve this in 2 ways (depending on how constrained your task actually is).
First, you can copy the string into arrays, instead of assigning the arrays to the results of the toCharArray method. You can achieve this with a simple loop, but I wouldn't recommend this approach, because you will end up with arrays of 80 characters, even if the strings contain less.
String firstSentence = reverseByCharacter(sentence1);
for (int i = 0; i < firstSentence.length(); i++) {
arr[0][i] = firstSentence.charAt(i);
}
Or:
char[] firstSentence = reverseByCharacter(sentence1).toCharArray();
for (int i = 0; i < firstSentence.length; i++) {
arr[0][i] = firstSentence[i];
}
Second, you can drop the assumption of the arrays' lengths in the printChar2DArray method. I recommend this approach, because it makes you code much more flexible. Your printChar2DArray method will then look like this:
public static String printChar2DArray(char[][] arr){
for (int x = 0; x < arr.length; x++) {
for (int y = 0; y < arr[x].length; y++) {
// just a print so it does not make new lines for every char
System.out.print(arr[x][y]);
}
}
return null;
}
You can see that I've substituted numbers with the length field, which can be accessed for any array.
Also, this way you don't need to initialize the inner arrays, because you reinitialize them in the next lines anyway.
char[][] arr = new char[3][];
arr[0] = reverseByCharacter(sentence1).toCharArray();
arr[1] = reverseByWord(sentence2).toCharArray();
arr[2] = change5thPosition(sentence3).toCharArray();
But this approach may not be suitable for your task, because then the sentences could be of any length, and they wouldn't be constained to 80 characters max.
UPDATE - To answer the question in the comment
To print a newline character you can use System.out.println() without parameters. It's better than putting the newline character into the arrays because it's not a logical part of the sentences.
So your for-loop in the printChar2DArray would look like this:
for (int x = 0; x < 3; x++) {
for (int y = 0; y < 80; y++) {
// just a print so it does not make new lines for every char
System.out.print(arr[x][y]);
}
System.out.println();
}
This is the code I am working upon. I dont know where I am going wrong.
package mcdcpairwise;
import java.io.*;
import java.util.*;
public class Permutation
{
public static void main(String[] args)
{
String a="000";
String b="|&";
for (int i=0; i < a.length(); i++){
if (i % 2 != 0){
a = a.substring(0,i-1) + b.substring(0,i-1). + a.substring(i, a.length()) + b.substring(i, b.length());
System.out.println(a);
}
}
}
}
The error I am facing is:
Exception in thread "main" java.lang.StringIndexOutOfBoundsException:
String index out of range: -2 at
java.lang.String.substring(String.java:1967) at
mcdcpairwise.Permutation.main(Permutation.java:13)
The output should be :
0|0&0
It isn't clear from your question exactly what your "rules" are for processing this. However, your output seems to simply insert a character between each character of your source a string.
Instead of using a substring, create a separate StringBuilder to add individual characters to. The code below produces the output you are looking for:
String string = "000";
StringBuilder output = new StringBuilder();
for (int i = 0; i < string.length(); i++) {
// Get current character in the string
char c = string.charAt(i);
// Add the current character to the output
output.append(c);
// If more characters exist, add the pipe
if (i != string.length() - 1) {
output.append("|");
}
}
System.out.println(output.toString());
The right code should be a.substring(0,i).
You can use String.toCharArray to get a char[] from a String. That way we can iterate more easily both String using an index.
String a="000";
String b="|&";
char[] arrayA = a.toCharArray();
char[] arrayB = b.toCharArray();
Then, all we have to do is to merge two array (from Strings) taking one character from both. Adding two conditions (one per array) to prevent any ArrayIndexOutOfBOundsException, we can insure we will merge two arrays.
StringBuilder sb = new StringBuilder();
//Add a char from both array (until we reach on of the limit)
int i = 0;
while( i < arrayA.length && i < arrayB.length){
sb.append(arrayA[i]).append(arrayB[i]);
++i;
}
Then we just need to add the remaining characters using a for loop on both arrays. Only one of those loop will be triggered (or none) since at least one previous condition (i < arrayA.length && i < arrayB.length) is already false.
//Add the rest of `a` if any
for(int j = i; j < arrayA.length; ++j){
sb.append(arrayA[j]);
}
//Add the rest of `b` if any
for(int j = i; j < arrayB.length; ++j){
sb.append(arrayB[j]);
}
System.out.println(sb.toString());
0|0&0
Here’s a one line solution:
System.out.println((a + b).replaceAll("(?<=.)(?=.{" + (a.length() - 1) + "}(.))|.(?=.{0," + (b.length() - 1) + "}$)", "$1"));
This works with all combinations of non-blank starting strings.
See live demo.
I'm very new to programming and I've spent some time looking for a way to do this that I can understand. I'm making a hangman game in java, it's all text based, and I've got almost the entire thing done. All I need is to replace a character array that holds the value of a random word to be replaced with dashes. So if the word was "java" I need to change that character array to "----". Since the word is chosen at random from a list, I have to find a way to use the length of the word to apply those dashes, but I'm not sure how.
Any help is appreciated!
A simple way to replace all the characters by '_' would be :
char[] charArray = {'W','O','R','D'};
Arrays.fill(charArray, '_');
I will give you an example based on what you have provided so far with java and ----:
public class Program {
public static void main(String[] args) {
String value = "java";
char[] array = value.toCharArray();
// Convert string to a char array.
for(int i = 0; i < value.length(); i++)
{
array[i] = '-';
}
// Loop over chars in the array.
for (char c : array) {
System.out.print(c);
}
}
}
OK, a few things that may be helpful in solving this task:
If you have a String you can easily get the length of that String like this:
String word = "java";
int lengthOfWord = word.length();
You can easily edit the contents of an array by accessing the individual elements:
char[] array = new char[4];
array[0] = '-';
array[1] = '_';
array[2] = '-';
array[3] = '_';
If you want to do something repeatedly and know how often you want to do that, using a for-loop is often a great idea. And you can use the counter within the loop. So for example:
int sum = 0;
for(int i = 0; i < 10; i++) {
sum += i;
}
So, combine those pieces of information and you can replace every element of that array. :-)
I am trying to read in a string from a file, extract individual characters and use those characters to fill a 2D char array. So far I have been able to do everything except fill the array. I keep getting an Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: error message. Any help would be appreciated. This is my first time working with 2D arrays. Thanks.
Here are the contents of the test.txt. Each word on a new line. The first 2 integers are the dimensions of the array
4 4
FILE
WITH
SOME
INFO
public class acsiiArt
{
public static void main(String[] args) throws IOException
{
File file = new File("test.txt");
Scanner inputFile = new Scanner(file);
int x = inputFile.nextInt();
int y = inputFile.nextInt();
while (inputFile.hasNext())
{
char [][] array = new char [x][y];
//char c = words.charAt(i);
for (int row =0; row<x;row++)
{
for (int col =0; col<y;col++)
{
String words = inputFile.nextLine();
for (int i=0; i<words.length(); i++)
array[x][y]=words.charAt(i);
}
}
}
}
}
for (int row =0; row<x;row++)
{
for (int col =0; col<y;col++)
{
String words = inputFile.nextLine();
for (int i=0; i<words.length(); i++)
array[x][y]=words.charAt(i);
}
}
The total number of indices in array is x * y. Below, you are filling all the possible indices
for (int row =0; row<x;row++)
{
for (int col =0; col<y;col++)
So when you add this:
for (int i=0; i<words.length(); i++)
you multiplying another factor words.length. So you need x * y * words.length number of indices, but you only have x * y. Thats why you're getting ArrayIndexOutOfBoudsException
I've seen problems like this and I'm assuming that x and y are being initialized to the first two characters which represent the number of rows and the number of columns. If that is the case, then third for loop for (int i=0; i<words.length(); i++) is unnecessary. You can just reffer to the col variable for the word at that point, since it should represent how many characters there are.
All of this is only applicable if the chars are in a rectangular pattern, meaning that there are the same number of columns in every row. Otherwise you will get an IndexOutOfBoundsError as soon as one of the lines is shorter than the the column value initially given.
Edit: If you're final 2d char array is not meant to be rectangular and instead "jagged," a different implementation is required. I'd recommend either a 2d arrayList (an arrayList of arrayLists).
Or you can keep your current implementation with the third for loop, but you have to be sure that the original x value represents the longest row/most amount of columns, and then you'd be able to deal with each row indivually with words.length. You'd also have to be fine with the extra portions of the lines that have a length>x having spaces initialized to null.
ArrayIndexOutOfBoundsException means you are using array beyond its limit. So in your case:
char [][] array = new char [x][y];
//char c = words.charAt(i);
for (int row =0; row<x;row++) {
for (int col =0; col<y;col++){
String words = inputFile.nextLine();
for (int i=0; i<words.length(); i++)
array[x][y]=words.charAt(i);
}
}
Problem may be because your array size is less then input words. problem is because you are putting extra loop, and your loop it self is not correct. Please seen code below.
So you can do 2 things.
change value of y large enough so that any word string can store.
rather than looping on size of word you can loop on your array size like.
.
for (int row =0; row<x;row++) {
String words = inputFile.nextLine();
int size = Math.min(words.length(),y);
for (int i=0; i< size; i++)
array[row][i]=words.charAt(i);
}
The easiest way to do this is with an ArrayList<char[]>. All you have to do is add a new char[] for each new line read:
ArrayList<char[]> chars = new ArrayList<>();
while (inputFile.hasNext()){
chars.add(inputFile.nextLine().toCharArray());
}
char[][] array = chars.toArray(new char[chars.size()][]);
An ArrayList is basically an array of changeable size. This code takes each line in the file, turns it into a char[], then adds it to the ArrayList. At the end, it converts the ArrayList<char[]> into a char[][].
If you can't or don't want to use ArrayList, you could always do this:
char[][] array = new char[1][];
int a = 0;
while(inputFile.hasNext()){
//read line and convert to char[]; store it.
array[a] = inputFile.nextLine().toCharArray();
//if there are more lines, increment the size of the array.
if (inputFile.hasNext()){
//create a clone array of the same length.
char[][] clone = new char[array.length][];
//copy elements from the array to the clone. Note that this can be
//done by index with a for loop
System.arraycopy(array, 0, clone, 0, array.length);
//make array a new array with an extra char[]
array = new char[array.length + 1][];
//copy elements back.
System.arraycopy(clone, 0, array, 0, clone.length);
a++;
}
}
If you know the dimensions of the array beforehand:
char[][] array = new char[dimension_1][];
int a = 0;
while (inputFile.hasNext()){
array[a] = inputFile.nextLine().toCharArray();
a++; //don't need to check if we need to add a new char[]
}
In response to comment:
We know that a char[][] cannot be printed with Arrays.toString() (if we want the contents) because we will get a lot of char[].toString(). However, a char[][] can be printed with one of the following methods:
public static String toString(char[][] array){
String toReturn = "[\n";
for (char[] cArray: array){
for (char c: cArray){
toReturn += c + ",";
}
toReturn += "\n";
}
return toReturn + "]";
}
I personally prefer this one (requires import java.util.Arrays):
public static String toString(char[][] array){
String toReturn = "[\n";
for (char[] cArray: array){
toReturn += Arrays.toString(cArray) + "\n";
}
return toReturn + "]";
}
i need to convert char array into string , the problem in doing this is......i need to convert the character in char array of particular length say k to string. ie, char array is "b" .b takes value dynamically.....for instance take as "p,a,p,e,r,s" now k value also dynamic ,for this word "k=5" ,and then only 4 characters in char array "b" should be converted into string...ie the string should print as "paper"........
the code what i have now is
for(int c=0;c<=k;c++)
{
System.out.print(b[c]);
}
str=new String(b);
System.out.println(str);
where b[c] prints correct value(in char array) as "paper". While converting to string str (in program) it prints as "papers" itself....can anyone give me solution for this?
You can use a different constructor of String that lets you specify the array along with the start point and number of characters to use.
In your case, you would try:
str = new String( b, 0, k );
char newArr[] = new char[k];
for (int i = 0; i < k; i++) {
newArr[i] = b[i];
System.out.print(b[i]); // print until the kth index
}
return new String(newArr);