How to return a String Array - java

My code is supposed to separate a given String and covert the chosen letters into # and separate and concatenate the words with the chosen letter. My problem is with one of the methods (allWordsWith) in my code, it won't allow me to return a String array. (p.s, the codes that run this one are irrelevant, I'm not supposed to edit those).
import java.util.Arrays;
import java.util.Scanner;
public class LipogramAnalyzer {
private String line;
public LipogramAnalyzer(String text){
line = text;
}
public String mark (char letter){
String replaceletters = line.replace(letter, '#');
return replaceletters;
}
public String[] allWordsWith (char letter){
String[] arr = line.split(" ");
for ( String ss : arr) {
String ary[] = {ss};
for(int i = 0; i < ary.length; i++){
int numindex = ss.indexOf(letter);
if (numindex != -1){
String result = ary[i];
return result;
}
}
}
}
}


"It won't allow me to return a String array"
Sure it will. You're attempting to return a String:
String result = ary[i];
return result;
Even though the return type is a string array:
public String[] allWordsWith (char letter){
You need to return an array, as allWordsWith implies you want multiple values.
But the bigger problem is that you are initializing the result array to a single element
String ary[] = {ss};
and thes lengths of arrays can't be changed after initialization. This means that ary.length in this loop
for(int i = 0; i < ary.length; i++){
will always equal one. That is not what you want.
In addition, you are searching the strings in the result array (ary), even though you just created it, meaning it has nothing in it--that is, all the values are null.
If you want a list of all the strings in line that have the letter in it, try
public String[] allWordsWith (char letter){
String[] asAllWordsInLine = line.split(" ");
java.util.ArrayList<String> alsAllWordsWithChar = new java.util.ArrayList<String>();
for ( String ss : asAllWordsInLine) {
if(ss.indexOf(letter) != -1) {
alsAllWordsWithChar.add(ss);
continue; //No need to check any more letters.
}
}
return alsAllWordsWithChar.toArray(new String[alsAllWordsWithChar.size()]);
}
I've changed the array to a list, since you can't know how many strings will have letter in it. A list can change size, an array can't. When no strings match, this returns an empty array, which is preferred over null. (more info)
I've also made the variable names more meaningful, and stopped checking a word after it matches a character (with continue, which short-circuits the current for-loop iteration).
Finally, the function is not returning anything until all strings have been analyzed, meaning after the for-loop completes. In your original code the return is inside the loop, meaning only the first string is returned.
A useful testing function:
public static final void main(String[] igno_red) {
testLine('b', "abc def ghi cba def ghi");
}
private static final void testLine(char c_letter, String s_line) {
System.out.println("Line: \"" + s_line + "\"");
String[] asAllWordsWith = (new LipogramAnalyzer(s_line)).allWordsWith(c_letter);
System.out.println("Words with '" + c_letter + "': " + Arrays.toString(asAllWordsWith));
}


Return the ary not ary[i]
for(int i = 0; i < ary.length; i++){
int numindex = ss.indexOf(letter);
if (numindex != -1){
String result = ary[i];
/*here*/ return ary;
}


You can return an array. Try return ary instead of return ary[i].
Also, your function must return something in all cases. In other words, you have to have a return statement after your for loops.


public String[] allWordsWith (char letter){
String[] arr = line.split(" ");
for ( String ss : arr) {
String ary[] = {ss};
for(int i = 0; i < ary.length; i++){
int numindex = ss.indexOf(letter);
if (numindex != -1){
String result = ary[i];
// or here return ary;
}
}
}
return ary;
}
Return the array


You are trying to return a String instead of String[] (String array)
Change the code:
if (numindex != -1) {
String result = ary[i];
return result;
}
To:
if (numindex != -1) {
return new String[]{ary[i]};
}
// afrer first for loop
return arr;


If you want to return a complete String-Array at once, I have modified your function (not tested):
public String[] allWordsWith (char letter){
String[] arr = line.split(" ");
String[] result = new String[ary.length];
for ( String ss : arr) {
String ary[] = {ss};
for(int i = 0; i < ary.length; i++){
int numindex = ss.indexOf(letter);
if (numindex != -1){
result[i] = ary[i];
}
}
}
return result;
}


As already said, you're returning a String instead of a String[]. Also note that your code will only ever return a single "word". I modified your code to add every word that contains your character and add it to a List. At the end of the loop the List is converted to a String[].
public String[] allWordsWith(char letter)
{
String[] arr = line.split(" ");
List<String> result = new ArrayList<>();
for (String ss : arr) {
int numindex = ss.indexOf(letter);
if (numindex != -1) {
result.add(ss);
}
}
return result.toArray(new String[result.size()]);
}

Related

How to search the largest string in an array of strings

I need to find the largest string from an array of strings and also want to make sure that the string which comes out should include only those chars which are defined in a separate string.
For eg: if an array of strings contains {"ABCAD","ABC","ABCFHG","AB"}
and another string S have chars "ABCD".
Then the largest string return here should be ABCAD as it contains only the characters defined in S.
public String findstring(String a, String[] arr)
{
String s="";
for(i=0; i<arr.length; i++)
{
//int m=0;
if(arr[i].length() > s.length())
{
s = arr[i];
}
}
for(j=0; j<s.length(); j++)
{
int m=0;
for(k=0; k<a.length(); k++)
{
if(m>0)
{
break;
}
if((s.charAt(j)==a.charAt(k)))
{
m++;
}
else
{
continue;
}
}
if(m==0)
{
List<String> list = new ArrayList<String>(Arrays.asList(arr));
list.remove(s);
arr = list.toArray(new String[0]);
findstring("ABCD", arr);
}
}
return s;
}
}
I am not receiving any error and getting the largest string as ABCFABCD whereas F needs to be excluded and largest string should be ABCAA.
Its skipping all the checks, don't know why?

You can do it in better way using Regex:
public String findstring(final String a, final String[] arr) {
String s = "";
// Created pattern of the characters available in the String
final Pattern p = Pattern.compile("^[" + a + "]*$");
for (int i = 0; i < arr.length; i++) {
if (p.matcher(arr[i]).matches()) {
if ("".equals(s)) {
s = arr[i];
} else if (arr[i].length() > s.length()) {
s = arr[i];
}
}
}
return s;
}

You make recursive call but just ignore the returned value.
Try add return on recursive findstring.
arr = list.toArray(new String[0]);
return findstring("ABCD", arr);

If you want to have the luxury of New & Much Better Java Powers with some elegant, readable and less lines of code... you can have a look at below snippet:
public static void main(String args[]) {
final String allowedChars = "ABCD";
final char[] chars = allowedChars.toCharArray();
String result = Stream.of("ABCAD","ABC","ABCFHG","AB")
.filter(s ->{
for(char c: chars){
if(!s.contains(c+""))
return false;
}
return true;
})
.max(Comparator.comparingInt(String::length))
.orElse("No Such Value Found");
System.out.println("Longes Valid String : " + result);
}
Explanation:
The code makes a Stream of String from arrays and filter only valid strings (Strings which are not containing the allowed characters will simply be removed from the further processing) and remaining Stream will be compared for the length (using Comparator), and finally, longest valid String will be returned.
There may be a case where all the strings in array/Stream would be invalid, in such case, the code will return the Message "No Such Value Found" as String, however you can throw an exception, or you can return some own value for your custom logic, or you can return null, etc.
I've intentionally kept the String message and gave you the hint about learning other methods present in Java Stream so that you can explore more.
Keep Coding... and feel the Power of New JAVA. :)

How to add multiple characters to one index in a Char Array?

Im currently trying to create a function where my input is a string such as "AABBCCDDEE" and the function outputs a String array "AA""BB""CC" and so on.
public static char[] stringSplitter(final String input) {
String[] strarray = new String[input.length()];
if (input == null) {
return null;
}
char[] chrarray = input.toCharArray();
char[] outputarray = new char[input.length()];
int j = 0;
for (int i = 0; i < chrarray.length; i++) {
char chr = chrarray[i];
System.out.print(chr);
outputarray[j] = chrarray[i]; //here i need to find a way to add the characters to the index at j if the preceding characters are equal
if (i + 1 < input.length() && chrarray[i + 1] != chr) {
j++;
outputarray[j] = chrarray[i + 1];
System.out.println(" ");
}
}
}

Arrays are fixed-length, so you can't do this with an array unless you allocate one with sufficient extra room up-front (which would require a pass through the string to find out how much extra room you needed).
Instead, consider using a StringBuilder for the output, which you can convert into a char array when you're done.

If I understood correctly, you want to split the characters in a string so that similar-consecutive characters stay together. If that's the case, here is how I would do it:
public static ArrayList<String> splitString(String str) {
ArrayList<String> output = new ArrayList<>();
String combo = "";
//iterates through all the characters in the input
for(char c: str.toCharArray()) {
//check if the current char is equal to the last added char
if(combo.length() > 0 && c != combo.charAt(combo.length() - 1)) {
output.add(combo);
combo = "";
}
combo += c;
}
output.add(combo); //adds the last character
return output;
}
Note that instead of using an array (has a fixed size) to store the output, I used an ArrayList, which has a variable size. Also, note that it's a list of strings (stores strings), not characters. The reason for this is that if it was a list of characters I wouldn't be able to store more than one character in the same index.
In each iteration of the loop, I check for equality between the current character and it's consecutive. The variable combo is used to temporarily store the characters (in a string) before they go to output.
Now, to print the results in a clear way:
public static void main(String[] args)
{
String input = "EEEE BCD DdA";
ArrayList<String> output = splitString(input);
System.out.print("[");
for(int i = 0; i < output.size(); i++) {
System.out.print("\"" + output.get(i) + "\"");
if(i != output.size()-1)
System.out.print(", ");
}
System.out.println("]");
}
The output when running the above code will be:
["EEEE", " ", "B", "C", "D", " ", "D", "d", "A"]

You can use an ArrayList of type String to store the consecutive letter Strings after splitting them. This code should work for you.
import java.util.*;
public class StringSplitter{
static ArrayList<String> splitString(String str)
{
ArrayList<String> result_list= new ArrayList<String>();
int last_index;
if(str == null)
{
return null;
}
else
{
while(str.length() != 0)
{
last_index = str.lastIndexOf(str.charAt(0));
result_list.add(str.substring(0, last_index+1));
str = str.substring(last_index+1);
}
}
return result_list;
}
public static void main(String[] args)
{
ArrayList<String> result = splitString("AABBCCDDEEE");
System.out.println(result);
}
}
I have used an ArrayList because it does not require you to fix a size while declaration.

Reverse String Method type mismatch error java

I am trying to use a method to reverse the characters in a string and I keep getting a type mismatch error. Any thoughts?
public static String userReverse (String userEntry3) {
String reverse = "";
for (int i = (userEntry3.length() -1); i >= 0 ; i--) {
reverse = System.out.println(userEntry3.charAt(i));
}
return reverse;
}

System.out.println is a void method. It returns nothing. So it cannot assigned back to a String variable
Your code is wrong.
If you want to reverse a string, you can use this:
public static String userReverse (String userEntry3) {
return new StringBuilder(userEntry3).reverse().toString()
}

Get rid of System.out.println and add a += to concatenate the new char
public static String userReverse (String userEntry3) {
String reverse = "";
for (int i = (userEntry3.length() -1); i >= 0 ; i--) {
reverse += userEntry3.charAt(i);
}
return reverse;
}
EDIT: As Tim said in the comments, StringBuilder can be used too (and is better practice than concatenating strings in a loop):
public static String userReverse (String userEntry3) {
StringBuilder reverse = new StringBuilder();
for (int i = (userEntry3.length() -1); i >= 0 ; i--) {
reverse.append(userEntry3.charAt(i));
}
return reverse.toString();
}

A more optimized way to reverse a string includes two pointer approach:
Use one pointer to start from the beginning and the other to start from the end. By the time they meet each other your string is already reversed
public static String userReverse (String userEntry3) {
int i = 0;
int j = userEntry3.length()-1;
StringBuilder myName = new StringBuilder(userEntry3);
for(; i < j ; i++,j--){
char temp = userEntry3.charAt(i);
myName.setCharAt(i,userEntry3.charAt(j));
myName.setCharAt(j,temp);
}
return myName.toString();
}

System.out.println() is a void method and it not return anything. you should try it this way,
public static String userReverse (String userEntry3) {
String reverse = "";
for (int i = (userEntry3.length() -1); i >= 0 ; i--) {
reverse += userEntry3.charAt(i).toString();
}
return reverse;
}

Java: Formatting issue. Grabbing unique characters from an array of strings and returning them

I'm having a problem getting the unique letters and digits out of an array of strings, and then returning them. I am having a formatting issue.
The given input is: ([abc, 123, efg]) and is supposed to return abcefg123,
however, mine returns: abc123efg
how can I fix this since arrays.sort() will end up putting the numbers first and not last?
Here is my method so far:
public static String getUniqueCharsAndDigits(String[] arr) {
String str = String.join(",", arr);
String myString = "";
myString = str.replaceAll("[^a-zA-Z0-9]", "");
for(int i = 0; i < str.length(); i++) {
if(Character.isLetterOrDigit((i))){
if(myString.indexOf(str.charAt(i)) == -1) {
myString = myString + str.charAt(i);
}
}
}
return myString;
}

What you want to do is create two strings, one with the letters, one with the digits.
public static String getUniqueCharsAndDigits(String[] arr) {
String str = String.join("", arr);
String myLetters, myDigits;
myLetters = myDigits = "";
for(int i = 0; i < str.length(); i++) {
char c = str.charAt(i);
if(Character.isLetter(c)){
if(myLetters.indexOf(c) == -1) {
myLetters += c;
}
} else if(Character.isDigit(c)){
if(myDigits.indexOf(c) == -1) {
myDigits += c;
}
}
}
//if they need to be sorted, sort each one individually here
return myLetters + myDigits;
}
I've modified your code and deleted the unnecessary parts of it.

I want to split string without using split function?

I want to split string without using split . can anybody solve my problem I am tried but
I cannot find the exact logic.

Since this seems to be a task designed as coding practice, I'll only guide. No code for you, sir, though the logic and the code aren't that far separated.
You will need to loop through each character of the string, and determine whether or not the character is the delimiter (comma or semicolon, for instance). If not, add it to the last element of the array you plan to return. If it is the delimiter, create a new empty string as the array's last element to start feeding your characters into.

I'm going to assume that this is homework, so I will only give snippets as hints:
Finding indices of all occurrences of a given substring
Here's an example of using indexOf with the fromIndex parameter to find all occurrences of a substring within a larger string:
String text = "012ab567ab0123ab";
// finding all occurrences forward: Method #1
for (int i = text.indexOf("ab"); i != -1; i = text.indexOf("ab", i+1)) {
System.out.println(i);
} // prints "3", "8", "14"
// finding all occurrences forward: Method #2
for (int i = -1; (i = text.indexOf("ab", i+1)) != -1; ) {
System.out.println(i);
} // prints "3", "8", "14"
String API links
int indexOf(String, int fromIndex)
Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. If no such occurrence exists, -1 is returned.
Related questions
Searching for one string in another string
Extracting substrings at given indices out of a string
This snippet extracts substring at given indices out of a string and puts them into a List<String>:
String text = "0123456789abcdefghij";
List<String> parts = new ArrayList<String>();
parts.add(text.substring(0, 5));
parts.add(text.substring(3, 7));
parts.add(text.substring(9, 13));
parts.add(text.substring(18, 20));
System.out.println(parts); // prints "[01234, 3456, 9abc, ij]"
String[] partsArray = parts.toArray(new String[0]);
Some key ideas:
Effective Java 2nd Edition, Item 25: Prefer lists to arrays
Works especially nicely if you don't know how many parts there'll be in advance
String API links
String substring(int beginIndex, int endIndex)
Returns a new string that is a substring of this string. The substring begins at the specified beginIndex and extends to the character at index endIndex - 1.
Related questions
Fill array with List data

You do now that most of the java standard libraries are open source
In this case you can start here

Use String tokenizer to split strings in Java without split:
import java.util.StringTokenizer;
public class tt {
public static void main(String a[]){
String s = "012ab567ab0123ab";
String delims = "ab ";
StringTokenizer st = new StringTokenizer(s, delims);
System.out.println("No of Token = " + st.countTokens());
while (st.hasMoreTokens()) {
System.out.println(st.nextToken());
}
}
}

This is the right answer
import java.util.StringTokenizer;
public class tt {
public static void main(String a[]){
String s = "012ab567ab0123ab";
String delims = "ab ";
StringTokenizer st = new StringTokenizer(s, delims);
System.out.println("No of Token = " + st.countTokens());
while (st.hasMoreTokens())
{
System.out.println(st.nextToken());
}
}
}

/**
* My method split without javas split.
* Return array with words after mySplit from two texts;
* Uses trim.
*/
public class NoJavaSplit {
public static void main(String[] args) {
String text1 = "Some text for example ";
String text2 = " Second sentences ";
System.out.println(Arrays.toString(mySplit(text1, text2)));
}
private static String [] mySplit(String text1, String text2) {
text1 = text1.trim() + " " + text2.trim() + " ";
char n = ' ';
int massValue = 0;
for (int i = 0; i < text1.length(); i++) {
if (text1.charAt(i) == n) {
massValue++;
}
}
String[] splitArray = new String[massValue];
for (int i = 0; i < splitArray.length; ) {
for (int j = 0; j < text1.length(); j++) {
if (text1.charAt(j) == n) {
splitArray[i] = text1.substring(0, j);
text1 = text1.substring(j + 1, text1.length());
j = 0;
i++;
}
}
return splitArray;
}
return null;
}
}

you can try, the way i did `{
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String str = sc.nextLine();
for(int i = 0; i <str.length();i++) {
if(str.charAt(i)==' ') { // whenever it found space it'll create separate words from string
System.out.println();
continue;
}
System.out.print(str.charAt(i));
}
sc.close();
}`

The logic is: go through the whole string starting from first character and whenever you find a space copy the last part to a new string.. not that hard?

The way to go is to define the function you need first. In this case, it would probably be:
String[] split(String s, String separator)
The return type doesn't have to be an array. It can also be a list:
List<String> split(String s, String separator)
The code would then be roughly as follows:
start at the beginning
find the next occurence of the delimiter
the substring between the end of the previous delimiter and the start of the current delimiter is added to the result
continue with step 2 until you have reached the end of the string
There are many fine points that you need to consider:
What happens if the string starts or ends with the delimiter?
What if multiple delimiters appear next to each other?
What should be the result of splitting the empty string? (1 empty field or 0 fields)

You can do it using Java standard libraries.
Say the delimiter is : and
String s = "Harry:Potter"
int a = s.find(delimiter);
and then add
s.substring(start, a)
to a new String array.
Keep doing this till your start < string length
Should be enough I guess.

public class MySplit {
public static String[] mySplit(String text,String delemeter){
java.util.List<String> parts = new java.util.ArrayList<String>();
text+=delemeter;
for (int i = text.indexOf(delemeter), j=0; i != -1;) {
parts.add(text.substring(j,i));
j=i+delemeter.length();
i = text.indexOf(delemeter,j);
}
return parts.toArray(new String[0]);
}
public static void main(String[] args) {
String str="012ab567ab0123ab";
String delemeter="ab";
String result[]=mySplit(str,delemeter);
for(String s:result)
System.out.println(s);
}
}

public class WithoutSpit_method {
public static void main(String arg[])
{
char[]str;
String s="Computer_software_developer_gautam";
String s1[];
for(int i=0;i<s.length()-1;)
{
int lengh=s.indexOf("_",i);
if(lengh==-1)
{
lengh=s.length();
}
System.out.print(" "+s.substring(i,lengh));
i=lengh+1;
}
}
}
Result: Computer software developer gautam

Here is my way of doing with Scanner;
import java.util.Scanner;
public class spilt {
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
System.out.print("Enter the String to be Spilted : ");
String st = input.nextLine();
Scanner str = new Scanner(st);
while (str.hasNext())
{
System.out.println(str.next());
}
}
}
Hope it Helps!!!!!

public class StringWitoutPre {
public static void main(String[] args) {
String str = "md taufique reja";
int len = str.length();
char ch[] = str.toCharArray();
String tmp = " ";
boolean flag = false;
for (int i = 0; i < str.length(); i++) {
if (ch[i] != ' ') {
tmp = tmp + ch[i];
flag = false;
} else {
flag = true;
}
if (flag || i == len - 1) {
System.out.println(tmp);
tmp = " ";
}
}
}
}

In Java8 we can use Pattern and get the things done in more easy way. Here is the code.
package com.company;
import java.util.regex.Pattern;
public class umeshtest {
public static void main(String a[]) {
String ss = "I'm Testing and testing the new feature";
Pattern.compile(" ").splitAsStream(ss).forEach(s -> System.out.println(s));
}
}

static void splitString(String s, int index) {
char[] firstPart = new char[index];
char[] secondPart = new char[s.length() - index];
int j = 0;
for (int i = 0; i < s.length(); i++) {
if (i < index) {
firstPart[i] = s.charAt(i);
} else {
secondPart[j] = s.charAt(i);
if (j < s.length()-index) {
j++;
}
}
}
System.out.println(firstPart);
System.out.println(secondPart);
}

import java.util.Scanner;
public class Split {
static Scanner in = new Scanner(System.in);
static void printArray(String[] array){
for (int i = 0; i < array.length; i++) {
if(i!=array.length-1)
System.out.print(array[i]+",");
else
System.out.println(array[i]);
}
}
static String delimeterTrim(String str){
char ch = str.charAt(str.length()-1);
if(ch=='.'||ch=='!'||ch==';'){
str = str.substring(0,str.length()-1);
}
return str;
}
private static String [] mySplit(String text, char reg, boolean delimiterTrim) {
if(delimiterTrim){
text = delimeterTrim(text);
}
text = text.trim() + " ";
int massValue = 0;
for (int i = 0; i < text.length(); i++) {
if (text.charAt(i) == reg) {
massValue++;
}
}
String[] splitArray = new String[massValue];
for (int i = 0; i < splitArray.length; ) {
for (int j = 0; j < text.length(); j++) {
if (text.charAt(j) == reg) {
splitArray[i] = text.substring(0, j);
text = text.substring(j + 1, text.length());
j = 0;
i++;
}
}
return splitArray;
}
return null;
}
public static void main(String[] args) {
System.out.println("Enter the sentence :");
String text = in.nextLine();
//System.out.println("Enter the regex character :");
//char regex = in.next().charAt(0);
System.out.println("Do you want to trim the delimeter ?");
String delch = in.next();
boolean ch = false;
if(delch.equalsIgnoreCase("yes")){
ch = true;
}
System.out.println("Output String array is : ");
printArray(mySplit(text,' ',ch));
}
}

Split a string without using split()
static String[] splitAString(String abc, char splitWith){
char[] ch=abc.toCharArray();
String temp="";
int j=0,length=0,size=0;
for(int i=0;i<abc.length();i++){
if(splitWith==abc.charAt(i)){
size++;
}
}
String[] arr=new String[size+1];
for(int i=0;i<ch.length;i++){
if(length>j){
j++;
temp="";
}
if(splitWith==ch[i]){
length++;
}else{
temp +=Character.toString(ch[i]);
}
arr[j]=temp;
}
return arr;
}
public static void main(String[] args) {
String[] arr=splitAString("abc-efg-ijk", '-');
for(int i=0;i<arr.length;i++){
System.out.println(arr[i]);
}
}
}

You cant split with out using split(). Your only other option is to get the strings char indexes and and get sub strings.

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