Java-Split characters from a String into an Array of Strings

Question

    import java.io.*;

    public class Test{
       public static void main(String args[]){
          String Str = new String("Welcome to Tutorialspoint.com and again some other random stuff in this string.");
          String[] result= new String[8];
          byte c=0b0;
          int i=0;
          int j=0;

          for (int a=0;a<7;a++){
              result[a]="";
          }
          for(i=0; j<Str.length(); j++){
              c=(byte)(Str.charAt(j));  
              result [i]+=(char)c;
              if (i<7){i++;}else{i=0;}
          }
          for (int a=0;a<8;a++){
              System.out.println(result[a]);
          }
       }
    }

The goal is to create 8 strings from the original string. String[0] will hold characters 0,8,16,...and so on. String[1] will hold characters 1,9,17,...and so on. I hope this is clear enough.

What I get with this code is something I cannot seem to overcome.

    Wtitdsemis
    eoa. or nt
    l lcam s r
    cTsogertti
    oupma auhn
    mto ionfig
    eoiantdfs.
    null rnn ho

Notice null in last line - I need this gone as string should start with ' rnn ho' just like this.

    Wtitdsemis
    eoa. or nt
    l lcam s r
    cTsogertti
    oupma auhn
    mto ionfig
    eoiantdfs.
     rnn ho

Would really appreciate if someone pointed out how to not get this output. This is a 'test' code for splitting a String that will hold values from -126 to 127 binary. Not all of them will be printable and I need them to still be split correctly. For the most part code seems to work except for those seemingly random 'null' strings in output.

I do not mind [null]=0 characters as long as they take 1 character space and not 4 in one String.

================================================================================== Initializing a<8 fixed this problem. But I did not even have time to read all other comments/answers. Did not expect such fast answers. THANK YOU ALL . I will up vote any relevant solution when I read them all and/or get reputation required.

================================================================================== FIXED!.

================================================================================== Selected answer of Ian McLaird as not only it fixed my 'silly' mistake but also showed me neater code and functionality that I did not know about. Regardless thank you all for comments and answers.

How about your first for loop? for (int a=0;a<=7;a++). You don't initialize that last String. — DaaaahWhoosh
– DaaaahWhoosh, Commented Dec 9, 2014 at 16:12
Why are you casting the return of charAt to byte and then casting the byte to a char? charAt already returns the type you want, and those conversions aren't safe. char is 16 bits in Java and byte is only 8. — Ian McLaird
– Ian McLaird, Commented Dec 9, 2014 at 16:23
@IanMcLaird I agree drop the casting to byte it is not doing anything but potentially creating problems. Also drop the casting to char because you already have the required type. — Code Whisperer
– Code Whisperer, Commented Dec 9, 2014 at 16:29
casting bytes and chars was a remnant of previous code where I used them to output result of byte^char. I will try to remove that if possible from further code if I can work with negative chars. Thanks again for suggestions. — iluzek
– iluzek, Commented Dec 9, 2014 at 16:52

Ian McLaird · Accepted Answer · 2014-12-09 16:48:53Z

How about this?

public class StringSplitter {
    public static void main(String[] args) {
        String str = new String("Welcome to Tutorialspoint.com and again some other random stuff in this string.");
        String[] result = new String[8];

        for (int i = 0; i < result.length; ++i) {
            result[i] = "";
        }

        char[] chars = str.toCharArray();
        for (int i = 0; i < chars.length; ++i) {
            result[i % result.length] += chars[i];
        }

        for (int i = 0; i < result.length; ++i) {
            System.out.println(result[i]);
        }
    }
}

Since your result array is already instantiated, it's safe to use the length property to initialize the elements to empty strings. Since you intend to process each character in the string, go ahead and just get it as an array, and then use the modulus operator to put each character into its proper place in the result array. As an added benefit, it's also safe against changing the length of the result array. Hard-coded loop sentinels are dangerous.

Output

Wtitdsemis
eoa. or nt
l lcam s r
cTsogertti
oupma auhn
mto ionfig
eoiantdfs.
 rnn ho

robm · Accepted Answer · 2014-12-09 16:31:39Z

0

From a quick glance at your code, the issue is that in your first for loop you're instantiating result[0] to result[6] and not instantiating result[7]. When you put for (int a = 0; a <7; a++) the loop will run until a = 6 - when it gets increased to 7 a<7 returns false so after the first for loop, result[7]==null

answered Dec 9, 2014 at 16:31

robm

1

1 Comment

Code Whisperer Over a year ago

As @DaaaahWhoosh wrote in the comments I agree with this. This seems to be the issue. Remember that 7 < 7 == false so result[7] does not get initialized. Always use i < array.length when in doubt. This will go over the whole array.

nitishagar · Accepted Answer · 2014-12-09 16:49:29Z

0

You can try the following:

import java.io.*;

public class Test{
  public static void main(String args[]){
    String Str = new String("Welcome to Tutorialspoint.com and again some other random stuff in this string.");

    String[] result = new String[8];

    for (int a = 0; a < result.length; a++)
       result[a] = "";

    char[] chars = str.toCharArray();
    for (int i = 0; i < chars.length; ++i) 
      result[i % result.length] += chars[i];

    for (int a = 0; a < result.length; a++)
      System.out.println(result[a]);
  }
}

Resulting output will be:

Wtitdsemis
eoa. or nt
l lcam s r
cTsogertti
oupma auhn
mto ionfig
eoiantdfs.
 rnn ho

edited Dec 9, 2014 at 16:49

answered Dec 9, 2014 at 16:43

nitishagar

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