CODEWITHSUNDEEP
javasubstring
Natsu Miko
Natsu Miko

Reputation: 61

How to substring and get previous character

I'm still very new to java and I search to replace a part of a string by another, except if the previous character of this string is C,V,M,G or W. I.e. if I get BILLE as input I want the output give me B.Y.E but if I get MILLE as input, I want MILLE as output.

Here what I've tried :

import java.util.HashMap;
import java.util.Map;



public class Phaille {
    static Map<String, String> phaille2 = new HashMap<String, String>();
    static {
        phaille2.put("ILL", ".Y.");
    }

    public static String phaille1(final String tampon){
        int position= tampon.indexOf("ILL");
        String sub=tampon.substring(position,tampon.length());


        if (position != -1 ){
            if(!(sub.endsWith("C"))){
                return phaille2.get(tampon);
            }

        }
        return tampon;
    }
}

But when i test with "CYRILLE", "CECILLE","ILL","CILLILLILL", the test gives to me

org.junit.ComparisonFailure: expected:<null> but was:<"CYR.Y.E">.

Upvotes: 0

Views: 210

Answers (2)

RealSkeptic
RealSkeptic

Reputation: 34618

The unit test output is a bit confusing (it should probably reverse the order of comparison to make the message reasonable). But basically, what it says is that you are returning null instead of returning CYR.Y.E.

You are returning null because of this line:

            return phaille2.get(tampon);

Your tampon is the original string CYRILLE. There is no item in phaille2 that matches the key CYRILLE (there is only an item for ILL), so the HashMap returns null, and this is what you return.

What you are doing is:

  • Looking for the position of ILL (that's good).
  • Finding the substring of tabmpon from that position forward (why? This will give you ILLE).
  • Checking to see if it begins with C (it will not, because it will always begin with ILL because that's what you were searching).
  • Returning the key based on tampon which I already told you does not exist in the hash table.

What you should do:

  • Find the position of the ILL as you do.

  • If the position is 0, replace ILL with what the HashTable contains for "ILL" (not tampon).

    • You should take the substring of tampon from before the position of ILL that you found,
    • Then add the replacement you got from the HashTable
    • Then add the substring of tampon from after the ILL.

    You'll probably need to play with this a bit to get the numbers right.

  • If the position is -1, there is no ILL in the number, and you need to return tampon as it is.
  • If the position is positive, look what is in the tampon.charAt(position-1), and decide whether you need to replace ILL (as I described above) or not.

I advise against using a regular expression, as I don't think it was taught at this point of your class, and it seems from your question that you are supposed to solve this with substring.

Upvotes: 0

TheLostMind
TheLostMind

Reputation: 36304

Try this code :

public static void main(String[] args) {
    String s1 = "BILLE";
    String s2 = "MILLE";
    String pattern = "(?<![WCVMG])ILL";
    System.out.println(s1.replaceAll(pattern, ".Y."));
    System.out.println(s2.replaceAll(pattern, ".Y."));
    System.out.println("CYRILLE".replaceAll(pattern, ".Y."));
    System.out.println("CILLILLILL".replaceAll(pattern, ".Y."));
}

O/P :

B.Y.E
MILLE
CYR.Y.E
CILL.Y..Y.

Upvotes: 3

Related Questions