在字符串字符之间添加空格

Question

I am working on a data encryption program. I have completed the encryption part but the decryption part is a bit tricky. In my program I convert plain text to something like this:

public String cipher_stream = new String("2057216345135157862323621293695559030383785129357667531585938249534612483932237388388135819035165204");

the above String is actually the encrypted form of the plain text

clearText = "hello this is bravo.";

now I want to add spaces to the String cipher_stream in a specific way. that is the first space should be inserted after 2 figure number then the second space should be inserted after three figure number then again a space should be inserted after 2 figure number and then again after three figure number.. the String cipher_stream will look like this after inserting spaces in a specific pattern

public String cipher_code = new String(20 572 16 345 13 515 78 623 23 621 29 369 55 590 30 383 78 512 93 576 67 531 58 593 82 495 34 612 48 393 22 373 88 388 13 581 90 351 65 204);

I tried very hard but cannot figure out how to do it... please if any one of you can help me. Thanks for helping

Answer 1

Here's some pseudo code

    boolean two = true;
    while (i < string.length())
    {
     if (two)
     {
     i = i + 2;
     string.insertSpace(i)
     two = false
     }
     else
     {
     i = i + 3;
     string.insertSpace(i)
     two = true;
     }
    }

You'll still have to make a method to insert the space or you could just hand jam it in there. Hope this helps.

Answer 2

Wrote something up really quick:

public class Test {

  public static String buildNewString(String input) {
        String output = "";
        String temp = "";
        int numbersToAppend = 2; //This will control how many numbers to append
        for (int i = 0; i < input.length(); i++) {
            if (numbersToAppend == 2) {
                temp = input.substring(i, i + numbersToAppend) + " ";
                output += temp;
                i += numbersToAppend - 1; //Skip the next 2
                numbersToAppend = 3; //Update to append 3 next time
            } else { //Must be 3
                temp = input.substring(i, i + numbersToAppend) + " ";
                output += temp;
                i += numbersToAppend - 1; //Skip the next 3
                numbersToAppend = 2; //Update to append 2 next time
            }
        }
        return output;
    }

    public static void main(String[] args) throws Exception {
        String cipher_stream = new String("2057216345135157862323621293695559030383785129357667531585938249534612483932237388388135819035165204");
        System.out.println("Old: " + cipher_stream);
        String newString = buildNewString(cipher_stream);
        System.out.println("New: " + newString);
    }
}

Sample output:

run:

Old: 2057216345135157862323621293695559030383785129357667531585938249534612483932237388388135819035165204

New: 20 572 16 345 13 515 78 623 23 621 29 369 55 590 30 383 78 512 93 576 67 531 58 593 82 495 34 612 48 393 22 373 88 388 13 581 90 351 65 204

BUILD SUCCESSFUL (total time: 0 seconds)

You could probably make it better by using Stringbuilder , I just wrote that up to show some logic. I don't have any logic to check if my substring will be out of bounds when I create it. You should probably add that since I assume not all numbers will work out perfectly like the example given. Cheers!

Answer 3

This method will do it:

private static String addSpaces(CharSequence input) {
    StringBuilder buf = new StringBuilder(input.length() * 7 / 5 + 1);
    for (int i = 0; i < input.length(); i++) {
        if (i != 0 && (i % 5 == 2 || i % 5 == 0))
            buf.append(' ');
        buf.append(input.charAt(i));
    }
    return buf.toString();
}

See IDEONE demo .

Answer 4

I wrote this code:

public class C {
    public static void main(String[] args) {
        String cipher_stream = "2057216345135157862323621293695559030383785129357667531585938249534612483932237388388135819035165204";
        System.out.println(cipher_stream);
        boolean twoOrThree = false; // false for 2, true for 3
        StringBuilder sb = new StringBuilder();
        String result = "";

        for (char c : cipher_stream.toCharArray()) {
            if (sb.length() == 0 || (sb.length() == 1 && twoOrThree))
                sb.append(c);
            else {
                sb.append(" ");
                sb.append(c);
                result += sb.toString();
                sb.setLength(0); // Clears the StringBuilder
                twoOrThree = twoOrThree ? false : true;
            }
        }
        System.out.println(result);
    }
}

Output:

2057216345135157862323621293695559030383785129357667531585938249534612483932237388388135819035165204

20 721 34 135 57 623 36 129 69 559 30 837 51 935 66 531 85 382 95 461 48 932 37 883 81 581 03 165

Answer 5

I would suggest take a string builder and keep appending to it and convert StringBuilder back to spring, this would save memory. Something like

StringBuilder sb = new StringBuilder();
int k = 2;
boolean switch = true;
int i = 0;
while(i < cipher_stream.length)
{
      if(k > 0)
      {
          sb.append(cipher_stream.charAt(i));
          k=k-1;
          i=i+1;
      }
      else if(k == 0)
      {
          sb.append(" ");
          switch = !switch;
          k=k-1;
          i = i+1;
      }
      else
      {
          if(switch == true)
                k = 2;
          else
                k = 3;
      }
}

String output = sb.toString();

Answer 6

  String cipher_stream = new String("2057216345135157862323621293695559030383785129357667531585938249534612483932237388388135819035165204");
  StringBuffer resultbuff=new StringBuffer("");
  for(int pl = 0;pl<cipher_stream.length();pl++)
  {
            //append space as per given condition...
            if (pl!= 0 && (pl % 5 == 2 || pl % 5 == 0))
                resultbuff.append(' ');
               resultbuff.append(cipher_stream.charAt(pl));


  }
  System.out.println(resultbuff);