Im trying to read strings such as combinations of Capital and lower case letters such as aSb for context free languages but I don't know how to read each piece of the string separately like read first a then S then b with various amounts of letters so not just 3 it can be any combination of letters.
If you want to read strings one letter at a time, you can use charAt() to convert to a char array.
for (int i = 0; i < myString.length(); i++) {
char c = myString.charAt(i);
// Do whatever you need with c
// If you want to convert it back to a String type, you can do
// String s = "" + c;
}
Using the character array:
char[] myCharArray = myString.toCharArray();
for (int i = 0; i < myCharArray.length; i++) {
char c = myCharArray[i];
}
Of course if you really just want the String type for some reason, you can use substring().
for (int i = 0; i < myString.length(); i++) {
String s = myString.substring(i, i+1);
}
Related
Following is the solution for finding the single differing additional alphabet between two strings.
public char findTheDifference(String s, String t) {
int sSum = 0;
int tSum = 0;
for(int i = 0; i < s.length(); i++){
sSum = sSum + Character.getNumericValue(s.charAt(i));
}
for(int j = 0 ; j < t.length(); j++){
tSum = tSum + Character.getNumericValue(t.charAt(j));
}
return (char)(tSum-sSum);
}
It returns '\u000e' instead of 'e'.
Example input:
String1 = "abcd"
String2 = "abecd"
Output= "e"
Questions:
1) Why is it returning '\u000e'? I understand that if I remove Character.getNumericValue within both for loops, I get 'e'. But I want to understand why using it adds \u000?
The issue is that Character.getNumericValue() converts a character to a number, using particular rules explained here.
In particular, the letters a, b, c, d, e that you're using get converted to the numbers 10, 11, 12, 13, 14 - this method assumes you intended them to be digits in a number system like hexadecimal.
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.
Following this question, I want to now code "6 choose 2" times "4 choose 2." By that I mean, lets say I have 6 characters "A B C D E F." The first time I choose any two characters to delete. The 2nd time I want to choose 2 different letters to delete and then I append the results of these two trials. Hence, I will receive 90("6 choose 2" times "4 choose 2") eight character strings. The characters in the pattern are from the same pattern {1,2,3,4,5, 6}. All the characters are unique and no repetition.
Here is what I have so far.
public String[] genDelPatterns(String design){
char[] data = design.toCharArray();
String[] deletionPatterns = new String[15];
int x = 0;
StringBuilder sb = new StringBuilder("");
int index = 0;
for(int i = 0; i < (6-1); i++){
for(int j = i+1; j < 6; j++){
for(int k= 0; k < 6; k++){
if((k != j) && (k != i))
sb.append(String.valueOf(data[k]));
}
deletionPatterns[x++] = sb.toString();
sb = new StringBuilder("");
}
}
return deletionPatterns;
}
public String[] gen8String(String[] pattern1, String[] pattern2){
String[] combinedPatterns = new String[225];
int k = 0;
for(int i = 0; i < 15; i++)
{
for(int j = 0; j < 15; j++)
combinedPatterns[k++] = pattern1[i] + pattern2[j];
}
return combinedPatterns;
}
I will be calling the methods like this:
gen8String(genDelPatterns("143256"), genDelPatterns("254316"));
Currently, I am generating all the possible 8 letter strings. But I want to only generate the 8 character strings according to the aforementioned specifications. I am really stuck on how I can elegantly do this multiplication. The only way I can think of is to make another method that does "4 choose 2" and then combine the 2 string arrays. But this seems very roundabout.
EDIT: An example of an 8 character string would be something like "14322516", given the inputs I have already entered when calling gen8String, (143256,254316). Note that the first 4 characters are derived from 143256 with the 5 and 6 deleted. But since I deleted 5 and 6 in the first trail, I am no longer allowed to delete the same things in the 2nd pattern. Hence, I deleted the 3 and 4 from the 2nd pattern.
you have a chain of methods , each one called a variation itself.
For so, my advice is to use a recursive method!
to achieve your goal you have to have a little experience with this solution.
A simple example of a method that exploits the recursion:
public static long factorial(int n) {
if (n == 1) return 1;
return n * factorial(n-1);
}
I can also suggest you to pass objects (constructed to perfection) for the method parameter, if is too complex to pass simple variables
This is the heart of this solution in my opinion.
While what you tried to do is definitely working, it seems you are looking for other way to implement it. Here is the skeleton of what I would do given the small constrains.
// Very pseudo code
// FOR(x,y,z) := for(int x=y; x<z;x++)
string removeCharacter(string s, int banA, int banB){
string ret = "";
FOR(i,1,7){
if(i != banA && i != banB){
ret += s[i];
}
}
return ret;
}
List<string> Generate(s1,s2){
List<string> ret = new List<string>();
FOR(i,1,7) FOR(j,i+1,7) FOR(m,1,7) FOR(n,m+1,7){
if(m != i && m != j && n != i && n != j){
string firstHalf = removeCharacter(s1,i,j);
string secondHalf = removeCharacter(s2,m,n);
ret.Add(firstHalf + secondHalf);
}
}
return ret;
}
This should generate all possible 8-characters string.
Here is the solution I came up with. Doesn't really take "mathematical" approach, I guess. But it does the job.
//generating a subset of 90 eight character strings (unique deletion patterns)
public static String[] gen8String(String[] pattern1, String[] pattern2){
String[] combinedSubset = new String[90]; //emty array for the subset of 90 strings
String combinedString = ""; //string holder for each combined string
int index = 0; //used for combinedSubset array
int present = 0; //used to check if all 6 characters are present
for(int i = 0; i < 15; i++){
for(int j = 0; j < 15; j++){
combinedString = pattern1[i] + pattern2[j]; //combine both 4 letter strings into 8 char length string
char[] parsedString = combinedString.toCharArray(); //parse into array
//check if all 6 characters are present
for(int k = 1; k <= 6; k++)
{
if(new String(parsedString).contains(k+"")) {
present++;
}
else
break;
//if all 6 are present, then add it to combined subset
if(present == 6)
combinedSubset[index++] = combinedString;
}
present = 0;
}
}
return combinedSubset;
}
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 want to get the frequency of all 128 signs (ASCII) with the simplest code possible. No imports.
I am writing in Java (Eclipse), starting off like this:
public class Text {
public static void main (String[] args) {
then I want to calculate the frequency of each sign with a loop (preferably for loop). I know how to do this for a specific sign, e.g. the sign 'a' which is 97:
int a = 0;
for (int i = 0; i < s.length(); i++) { // s is a String
if (s.charAt(i) == 'a') {
a += 1;
}
}
System.out.println("a: " + a);
I need to create a table of all the signs (e.g. int[] p = new int p[1,2,3] - only for a string (or char?)) assign each index its number and then let a loop write out all the sign frequencies.
All this should be done only with loops and commands: .length, charAt().
Simply:
final String s = "Hello World!";
final int frequencies[] = new int[128];
for (int i = 0; i < s.length(); i++) {
final int ascii = (int) s.charAt(i);
frequencies[ascii]++;
}
(in response to user2974951's "answer")
That's the String representation of the array. Try printing with a loop instead:
for(int i = 0; i < frequencies.length; i++) {
System.out.println(frequencies[i]);
}
You can also try System.out.println(Arrays.toString(frequencies)); but that might look a bit ugly given the large amount of ASCII characters you are considering.