How to return a String Array

Question

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;
                    }
                }
        }
    }
}

Answer 1

"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));  
}  

Answer 2

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()]);
}

Answer 3

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;
}

Answer 4

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;

Answer 5

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

Answer 6

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;
                        }

Answer 7

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.