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

Question

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.

Please learn how to enter code. It's not hard, either indent 4 spaces or use the {} button in the embedded editor. — Jim Garrison
– Jim Garrison, Commented Nov 30, 2017 at 19:30
size is null because your array seems too big? why not only print the value if it is not null — John Kane
– John Kane, Commented Nov 30, 2017 at 19:41
@JohnKane array size is not big. I have used a for loop to exactly get the size of the result I want. — mkabhishek
– mkabhishek, Commented Nov 30, 2017 at 19:44
appreciate all the answers. understood my mistake in the code. — mkabhishek
– mkabhishek, Commented Dec 4, 2017 at 19:29

xtra · Accepted Answer · 2017-11-30 19:58:01Z

1

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
}

answered Nov 30, 2017 at 19:58

xtra

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Comments

Oleg Cherednik · Accepted Answer · 2017-11-30 20:06:27Z

1

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"));
}

}

edited Nov 30, 2017 at 20:06

Oleg Cherednik

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answered Nov 30, 2017 at 19:50

zlakad

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Comments

Dora · Accepted Answer · 2017-11-30 20:08:33Z

1

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.

answered Nov 30, 2017 at 20:08

Dora

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Comments

sanju · Accepted Answer · 2017-11-30 22:14:06Z

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;

}

pkn · Accepted Answer · 2017-11-30 19:57:45Z

0

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
}

answered Nov 30, 2017 at 19:57

pkn

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Comments

Krzysztof Kaszkowiak · Accepted Answer · 2017-11-30 20:06:22Z

0

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

edited Nov 30, 2017 at 20:06

answered Nov 30, 2017 at 19:54

Krzysztof Kaszkowiak

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