Develop Reference

how to split a string by using charAt and string.length()

only allow charAt method and length method . Thank you so much!
void runApp() {
String str = "345, 688"; //->"345" "688"
String value = strCut(str);
}
String strCut(String str) {
int result = 0;
for (int i = 0; i < str.length(); i++) {
if (str.charAt(3) == ',') {
what should i write here ? ?
}

Your code needs some refactoring, try this:
void runApp() {
String str = "345, 688"; //->"345" "688"
String value = strCut(str);
}
String strCut(String str) {
int result = 0;
for (int i = 0; i < str.length(); i++) {
int cutStringIndex;
if (str.charAt(i) == ',') {
cutStringIndex = i;
}
for (int i = 0; i < cutStringIndex(); i++) {
String cutStringOne = "";
cutStringOne = cutStringOne + str.charAt(i);
}
for (int i = cutStringIndex() + 1; i < str.length(); i++) {
String cutStringTwo = "";
cutStringTwo = cutStringTwo + str.charAt(i);
}
cutString = cutStringOne + " " + cutStringTwo;
return cutString;
}
This will take out the comma which appears to be what you were looking for. I only used the two methods you asked for. Essentially this code gets the index of the comma, then reconstructs the two parts of the strings until it reaches the point of the comma, and skips over it. It may need some minor tweaks for your situation but this should be what you're looking for.

It can be done like this, Suppose String s="200,300,450,600" and you have to split given string using charAt() and string.length() method then first add ',' at the end of the string as given in the code below.
String s="200,300,450,600,",str="";
for(int i=0;i<s.length();i++){
char ch=s.charAt(i);
if(ch!=','){ //checking if particular character is not ','
str+=ch; //storing it in str string
}
else{
System.out.println(str); //printing each string before ',' is found
str="";
}
}
The output of above code will be:200
300
450
600(all the numbers will be printed on next line)

If you want to use only charAt and string.length() then you should try this
void runApp{
String str = "345, 688, 123";
String values[] = strCut(str); //values[0] = 345, values[1] = 688, values[2] = 123
for(String value : values){
System.out.print(value + " ");
}
}
String[] strCut(String str) {
int elements = 1;
int index = 0;
for(int i = 0; i < str.length(); i++){
if(str.charAt(i) == ',')
elements++;
}
String result[] = new String[elements];
for(int i = 0; i < result.length; i++)
result[i] = "";
for (int i = 0; i < str.length(); i++) {
if (str.charAt(i) != ',') {
if(str.charAt(i) != ' ')
result[index] = result[index] + str.charAt(i);
}
else index++;
}
return result;
}

You can do it as follows:
public class Main {
public static void main(String[] args) {
// Test
runApp();
}
static void runApp() {
String str = "345, 688"; // Expected->"345" "688"
String value = strCut(str);
System.out.println(value);// Display the result
}
static String strCut(String str) {
// Initialise result with a "
String result = "\"";
for (int i = 0; i < str.length(); i++) {
if (str.charAt(i) == ',') {// Check char at the index, i
// Add " at the end of one number and again " at the start of the next
result += "\" \"";
} else if (str.charAt(i) != ' ') {
result += str.charAt(i);
}
}
// Add " at the end
result += "\"";
// Finally, return result
return result;
}
}
Output:
"345" "688"

if you must want to make use of charAt() then do like below..
ArrayList<String> stringArr= new ArrayList<String>();
int startindex=0;
for (int i = 0; i < str.length(); i++)
{
if (str.charAt(i) == ',')
{
String partString = str.substring(startindex, i) ;
startindex=i+1;
stringArr.add(partString);
}
}
String lastString = str.substring(startindex, str.length()) ;
stringArr.add(lastString);
OR
You can simply use split method like below
String[] parts = string.split(",");
String part1 = parts[0]; // 345
String part2 = parts[1]; // 688

You can achieve it by simply doing this,
This will give you the desired result.
String str = "345,688";
ArrayList<String> stringArray = new ArrayList<>();
int startindex=0;
for (int i = 0; i < str.length(); i++) {
if(str.charAt(i) == ',') {
String subStr = str.substring(startindex, i);
startindex = i+1;
stringArray.add(subStr);
}
}
stringArray.add(str.substring(startindex));

parsing/converting task with characters and numbers within

It is necessary to repeat the character, as many times as the number behind it.
They are positive integer numbers.
case #1
input: "abc3leson11"
output: "abccclesonnnnnnnnnnn"
I already finish it in the following way:
String a = "abbc2kd3ijkl40ggg2H5uu";
String s = a + "*";
String numS = "";
int cnt = 0;
for (int i = 0; i < s.length(); i++) {
char ch = s.charAt(i);
if (Character.isDigit(ch)) {
numS = numS + ch;
cnt++;
} else {
cnt++;
try {
for (int j = 0; j < Integer.parseInt(numS); j++) {
System.out.print(s.charAt(i - cnt));
}
if (i != s.length() - 1 && !Character.isDigit(s.charAt(i + 1))) {
System.out.print(s.charAt(i));
}
} catch (Exception e) {
if (i != s.length() - 1 && !Character.isDigit(s.charAt(i + 1))) {
System.out.print(s.charAt(i));
}
}
cnt = 0;
numS = "";
}
}
But I wonder is there some better solution with less and cleaner code?

Could you take a look below? I'm using a library from StringUtils from Apache Common Utils to repeat character:
public class MicsTest {
public static void main(String[] args) {
String input = "abc3leson11";
String output = input;
Pattern p = Pattern.compile("\\d+");
Matcher m = p.matcher(input);
while (m.find()) {
int number = Integer.valueOf(m.group());
char repeatedChar = input.charAt(m.start()-1);
output = output.replaceFirst(m.group(), StringUtils.repeat(repeatedChar, number));
}
System.out.println(output);
}
}
In case you don't want to use StringUtils. You can use the below custom method to achieve the same effect:
public static String repeat(char c, int times) {
char[] chars = new char[times];
Arrays.fill(chars, c);
return new String(chars);
}

Using java basic string regx should make it more terse as follows:
public class He1 {
private static final Pattern pattern = Pattern.compile("[a-zA-Z]+(\\d+).*");
// match the number between or the last using regx;
public static void main(String... args) {
String s = "abc3leson11";
System.out.println(parse(s));
s = "abbc2kd3ijkl40ggg2H5uu";
System.out.println(parse(s));
}
private static String parse(String s) {
Matcher matcher = pattern.matcher(s);
while (matcher.find()) {
int num = Integer.valueOf(matcher.group(1));
char prev = s.charAt(s.indexOf(String.valueOf(num)) - 1);
// locate the char before the number;
String repeated = new String(new char[num-1]).replace('\0', prev);
// since the prev is not deleted, we have to decrement the repeating number by 1;
s = s.replaceFirst(String.valueOf(num), repeated);
matcher = pattern.matcher(s);
}
return s;
}
}
And the output should be:
abccclesonnnnnnnnnnn
abbcckdddijkllllllllllllllllllllllllllllllllllllllllggggHHHHHuu

String g(String a){
String result = "";
String[] array = a.split("(?<=\\D)(?=\\d)|(?<=\\d)(?=\\D)");
//System.out.println(java.util.Arrays.toString(array));
for(int i=0; i<array.length; i++){
String part = array[i];
result += part;
if(++i == array.length){
break;
}
char charToRepeat = part.charAt(part.length() - 1);
result += repeat(charToRepeat+"", new Integer(array[i]) - 1);
}
return result;
}
// In Java 11 this could be removed and replaced with the builtin `str.repeat(amount)`
String repeat(String str, int amount){
return new String(new char[amount]).replace("\0", str);
}
Try it online.
Explanation:
The split will split the letters and numbers:
abbc2kd3ijkl40ggg2H5uu would become ["abbc", "2", "kd", "3", "ijkl", "40", "ggg", "2", "H", "5", "uu"]
We then loop over the parts and add any strings as is to the result.
We then increase i by 1 first and if we're done (after the "uu") in the array above, it will break the loop.
If not the increase of i will put us at a number. So it will repeat the last character of the part x amount of times, where x is the number we found minus 1.

Here is another solution:
String str = "abbc2kd3ijkl40ggg2H5uu";
String[] part = str.split("(?<=\\d)(?=\\D)|(?=\\d)(?<=\\D)");
String res = "";
for(int i=0; i < part.length; i++){
if(i%2 == 0){
res = res + part[i];
}else {
res = res + StringUtils.repeat(part[i-1].charAt(part[i-1].length()-1),Integer.parseInt(part[i])-1);
}
}
System.out.println(res);

Yet another solution :
public static String getCustomizedString(String input) {
ArrayList<String > letters = new ArrayList<>(Arrays.asList(input.split("(\\d)")));
letters.removeAll(Arrays.asList(""));
ArrayList<String > digits = new ArrayList<>(Arrays.asList(input.split("(\\D)")));
digits.removeAll(Arrays.asList(""));
for(int i=0; i< digits.size(); i++) {
int iteration = Integer.valueOf(digits.get(i));
String letter = letters.get(i);
char c = letter.charAt(letter.length()-1);
for (int j = 0; j<iteration -1 ; j++) {
letters.set(i,letters.get(i).concat(String.valueOf(c)));
}
}
String finalResult = "";
for (String str : letters) {
finalResult += str;
}
return finalResult;
}
The usage:
public static void main(String[] args) {
String testString1 = "abbc2kd3ijkl40ggg2H5uu";
String testString2 = "abc3leson11";
System.out.println(getCustomizedString(testString1));
System.out.println(getCustomizedString(testString2));
}
And the result:
abbcckdddijkllllllllllllllllllllllllllllllllllllllllggggHHHHHuu
abccclesonnnnnnnnnnn

Remove null from unused space of StringArray when converting to a string in Java

I was working on a Java coding problem and encountered the following issue.
Input: A String -> "Code"
Output Expected: A string -> CCoCodCode
My Code snippet: (Note: In comments I have written what I expect upon passing the string)
public String stringSplosion(String str) { // string Say 'Code'
String join = "", values = "";
String gotIt = "";
int n = str.length(); // 4
int size = 0;
for (int i = n; i >= 1; i--) {
size = size + n; // 4+3+2+1=10
}
String[] result = new String[size];
for (int i = 0; i < str.length(); i++) {
values = str.substring(i, i + 1);
join = join + values;
result[i] = join;
}
for (String s : result) {
gotIt = gotIt + s;
}
return gotIt; // Expected output: CCoCodCode
}
Output I am getting:
CCoCodCodenullnullnullnullnullnullnullnullnullnullnullnull
Why is null getting stored although I have reduced the size and how can I remove it?
NOTE: I need to solve this using arrays. I know it is much easier using List.

If you want to keep the current structure of your code, get rid of the first for loop.
And create String[] array = new String[n]
public static String stringSplosion(String str) { // string Say 'Code'
String join = "", values = "";
String gotIt = "";
int n = str.length(); // 4
String[] result = new String[n]; //you want your String array to contain 4 strings
for (int i = 0; i < str.length(); i++) {
values = str.substring(i, i + 1);
join = join + values;
result[i] = join;
}
for (String s : result) {
gotIt = gotIt + s;
}
return gotIt; // Expected output: CCoCodCode
}

public class Answer {
public static String answer(String input){
StringBuilder sb = new StringBuilder(((input.length() + 1) * input.length()) / 2);
for (int i = 1; i <= input.length(); i++) {
sb.append(input.substring(0, i));
}
return sb.toString();
}
public static void main(String[] args) {
System.out.println(answer("Code"));
}
}

Below statements are not required:
int size = 0;
for (int i = n; i >= 1; i--) {
size = size + n; // 4+3+2+1=10
}
You just need to change the array size from
String[] result = new String[size];
to
String[] result = new String[n];
for your program to give the expected output.

If I understand ur problem correctly to print the pattern then u can use below code,
public String printPattern(String input){
//Holds the iteration value by index
int previous=0;
//It holds the result characters
String result=null;
StringBuilder strBuilder=new StringBuilder();
//first loop to iterate only till input string length
for(int i=0;i<input.length();i++){
//checking iteration lenght with input string length
if(previous<input.length()){
//incrementing iteration for reading characters from input string
previous++;
//main loop for previous iteration value check and iterate
for(int j=0;j<previous;j++){
//converting string to Character array
char a []=input.toCharArray();
//using string builder to build the string from characters
strBuilder.append((a[j]));
//setting the value to stringbuilder by converting it in string
result=strBuilder.toString();
}
}
}
return result;
}

Size should be the length of string. Code's length is 4. Code will produce {C, Co, Cod, Code}.
public String stringSplosion(String str) { // string Say 'Code'
String join = "", values = "";
String gotIt = "";
int n = str.length(); // 4
String[] result = new String[n];
for (int i = 0; i < str.length(); i++) {
values = str.substring(i, i + 1);
join = join + values;
result[i] = join;
}
System.out.println(Arrays.toString(result));
for (String s : result) {
gotIt = gotIt + s;
}
return gotIt; // Expected output: CCoCodCode
}

String input = "Code";
String output[] = IntStream.range(0, input.length()+1)
.mapToObj(i -> input.substring(0, i))
.toArray(String[]::new);

Finding patterns in strings using basic Java methods

say we have a string with these characters
"ABGCCFFGTBG"
then we have another string with characters "GECCCDOABG"
So the pattern is the prefix and suffix but if your given strings larger then this but have common prefix and suffix patterns how to pull those out into a substring in java. Keep in mind we dont always know the characters in the string were getting we just know there is a pattern in it.
my start is something like this
for(int i = 0. i < strA.length(); i++)
{
for(int j = 0; j < strB.length(); j++)
{
if(strA.charAt(i) == strB.charAt(j))
{
String subPattern = strA.substring(0,i);
String subPattern2 = strB.substring(0,j);
}
}
}
but this doesn't work. Any ideas?

Try to select best-matched pattern at first:
public static void main(String[] args) {
String strA = "ABGCCFFGTBG";
String strB = "GECCCDOABG";
System.out.println("Pattern: " + findPattern(strA, strB));
}
public static String findPattern(String strA, String strB) {
for (int length = Math.min(strA.length(), strB.length()); length > 0; length--) {
for (int i = 0; i <= strA.length() - length; i++) {
String pattern = strA.substring(i, i + length);
if (strB.contains(pattern)) {
return pattern;
}
}
}
throw new NoSuchElementException("No common pattern between " + strA + " and " + strB);
}
Output:
Pattern: ABG

this solution will find a pattern, no matter where it is in the string:
public static void main(String[] args) {
String strA = "uioABCDqwert";
String strB = "yxcvABCDwrk";
StringBuilder sb = new StringBuilder();
for (int i = 0; i < strA.length(); i++) {
for (int j = 0; j < strB.length(); j++) {
if (strA.charAt(i) == strB.charAt(j)) {
sb.append(strB.charAt(j));
i++;
}
}
if (sb.length() > 0)
break;
}
System.out.println(sb.toString());
}
this should give you an idea how it could be done

Fancy looping in Java

I have a problem wherein I have two strings, the length of one of which I will know only upon execution of my function. I want to write my function such that it would take these two stings and based upon which one is longer, compute a final string as under -
finalString = longerStringChars1AND2
+ shorterStringChar1
+ longerStringChars3and4
+ shorterStringChar2
+ longerStringChars5AND6
...and so on till the time the SHORTER STRING ENDS.
Once the shorter string ends, I want to append the remaining characters of the longer string to the final string, and exit. I have written some code, but there is too much looping for my liking. Any suggestions?
Here is the code I wrote - very basic -
public static byte [] generateStringToConvert(String a, String b){
(String b's length is always known to be 14.)
StringBuffer stringToConvert = new StringBuffer();
int longer = (a.length()>14) ? a.length() : 14;
int shorter = (longer > 14) ? 14 : a.length();
int iteratorForLonger = 0;
int iteratorForShorter = 0;
while(iteratorForLonger < longer) {
int count = 2;
while(count>0){
stringToConvert.append(b.charAt(iteratorForLonger));
iteratorForLonger++;
count--;
}
if(iteratorForShorter < shorter && iteratorForLonger >= longer){
iteratorForLonger = 0;
}
if(iteratorForShorter<shorter){
stringToConvert.append(a.charAt(iteratorForShorter));
iteratorForShorter++;
}
else{
break;
}
}
if(stringToConvert.length()<32 | iteratorForLonger<b.length()){
String remainingString = b.substring(iteratorForLonger);
stringToConvert.append(remainingString);
}
System.out.println(stringToConvert);
return stringToConvert.toString().getBytes();
}

You can use StringBuilder to achieve this. Please find below source code.
public static void main(String[] args) throws InterruptedException {
int MAX_ALLOWED_LENGTH = 14;
String str1 = "yyyyyyyyyyyyyyyy";
String str2 = "xxxxxx";
StringBuilder builder = new StringBuilder(MAX_ALLOWED_LENGTH);
builder.append(str1);
char[] shortChar = str2.toCharArray();
int index = 2;
for (int charCount = 0; charCount < shortChar.length;) {
if (index < builder.length()) {
// insert 1 character from short string to long string
builder.insert(index, shortChar, charCount, 1);
}
// 2+1 as insertion index is increased after after insertion
index = index + 3;
charCount = charCount + 1;
}
String trimmedString = builder.substring(0, MAX_ALLOWED_LENGTH);
System.out.println(trimmedString);
}
Output
yyxyyxyyxyyxyy

String one = "longwordorsomething";
String two = "short";
String shortString = "";
String longString = "";
if(one.length() > two.length()) {
shortString = two;
longString = one;
} else {
shortString = one;
longString = two;
}
StringBuilder newString = new StringBuilder();
int j = 0;
for(int i = 0; i < shortString.length(); i++) {
if((j + 2) < longString.length()) {
newString.append(longString.substring(j, j + 2));
j += 2;
}
newString.append(shortString.substring(i, i + 1));
}
// Append last part
newString.append(longString.substring(j));
System.out.println(newString);