getSandwich java challenge

public String getSandwich(String str) {
  return str.replaceFirst("(?:(?!bread).)*(?:bread(.*)bread)?.*","$1");
}

public String getSandwich(String str) {
int breadCount=0;
for(int i=0;i<str.length();i++)
{

breadCount++;
}
if(breadCount>1){
return str.replaceAll(".*bread.*","");
}
else if(breadCount==1){
return "";
}
else
return "aaa";
}

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why above fails below

Expected      Run            
getSandwich("breadjambread") → "jam"      ""      X         
getSandwich("xxbreadjambreadyy") → "jam"      ""      X         
getSandwich("xxbreadyy") → ""      ""      OK         
getSandwich("xxbreadbreadjambreadyy") → "breadjam"      ""      X         
getSandwich("breadAbread") → "A"      ""      X         
getSandwich("breadbread") → ""      ""      OK         
getSandwich("abcbreaz") → ""      "abcbreaz"      X         
getSandwich("xyz") → ""      "xyz"      X         
getSandwich("") → ""      "aaa"      X         
getSandwich("breadbreaxbread") → "breax"      ""      X         
getSandwich("breaxbreadybread") → "y"      ""      X         
getSandwich("breadbreadbreadbread") → "breadbread"      ""      X         
other tests

public String getSandwich(String str) {
int breadCount=0;
for(int i=0;i<str.length();i++)
{

breadCount++;
}
if(breadCount>1){
return str.replaceAll("bread","");
}
else if(breadCount==1){
return "";
}
else
return "aaa";
}

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above fails some too

Expected      Run            
getSandwich("breadjambread") → "jam"      "jam"      OK         
getSandwich("xxbreadjambreadyy") → "jam"      "xxjamyy"      X         
getSandwich("xxbreadyy") → ""      "xxyy"      X         
getSandwich("xxbreadbreadjambreadyy") → "breadjam"      "xxjamyy"      X         
getSandwich("breadAbread") → "A"      "A"      OK         
getSandwich("breadbread") → ""      ""      OK         
getSandwich("abcbreaz") → ""      "abcbreaz"      X         
getSandwich("xyz") → ""      "xyz"      X         
getSandwich("") → ""      "aaa"      X         
getSandwich("breadbreaxbread") → "breax"      "breax"      OK         
getSandwich("breaxbreadybread") → "y"      "breaxy"      X         
getSandwich("breadbreadbreadbread") → "breadbread"      ""      X         
other tests
X

  return str.replaceFirst("(.*?bread(.*)bread)?.*","$2");

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what is the logic and meaning of above solution
replacing all characters before(.*?bread) and after bread(bread)?.*",) with $2?

In a replacement string, $2 represents the string matched by the 2nd pair of capturing parentheses.

return str.indexOf("bread") == str.lastIndexOf("bread") ? "" :
       str.substring(str.indexOf("bread") + 5, str.lastIndexOf("bread"));

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public String getSandwich(String str) {
    int first=Math.min(str.indexOf("bread")+5,str.length());
    int last=Math.max(str.lastIndexOf("bread"),first);
    return str.substring(first,last);
}

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str.substring(str.indexOf("bread") + 5

why we are adding to 5

in below solution

public class HelloWorld{
     public static void main(String []args){
        System.out.println("Hello World"+ getSandwich("breadjambread"));
     }
     
     public  static String getSandwich(String str) {

return str.indexOf("bread") == str.lastIndexOf("bread") ? "" : str.substring(str.indexOf("bread") + 5, str.lastIndexOf("bread"));
}

}

why we are adding 5

To get from the index of the beginning of "bread" to the index of the end of "bread"

public class HelloWorld{
     public static void main(String []args){
        System.out.println("Hello World"+ getSandwich("breadAbread"));
     }
     
     public  static String getSandwich(String str) {
    	 System.out.println("  is-->"+ str.indexOf("bread"));
    	 System.out.println("  last is-->"+ str.lastIndexOf("bread"));

return str.indexOf("bread") == str.lastIndexOf("bread") ? "" 
		: str.substring(str.indexOf("bread") + 5, str.lastIndexOf("bread"));
}

}

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above gave below right output.

  is-->0
  last is-->6
Hello WorldA


so we are checking indexOf ==lastIndex which means only one bread then return ""
otherwise we are basically asking to print middle sandwitched part using

str.substring(str.indexOf("bread") + 5, str.lastIndexOf("bread"))

public String getSandwich(String str) {
  return str.replaceFirst("(?:(?!bread).)*(?:bread(.*)bread)?.*","$1");
}

how to test above in regex101 site?

i should only take as bolded above by ignoring all the java statements?

https://regex101.com/r/gT1yH8/1

why we need substitution variable as

$1

if i remove that how to re run
to see new output

please advise

https://regex101.com/r/gT1yH8/2

as attached i am not able to see output now at bottom most section.


How to get output.

what is the button i have to click to see output?

https://regex101.com/r/gT1yH8/2
jam.png

what is meaning of $1 in substitution?

https://regex101.com/r/gT1yH8/3

Substitution

Contents in capture group 1  $1

This will return a string with the contents from the first capture group. The number, in this case 1, can be any number as long as it corresponds to a valid capture group.

what is difference between capturing group and substitution. are both same?

A capturing group is a pair of (parentheses) in the regular expression -- except when the pattern in the parentheses starts with ?

A substitution is the second argument in a replaceFirst(pattern,substitution) call in Java,
or what you enter in the Substitution input box in regex101.com

In a Java (or regex101) substitution, "$1" gets replaced by what was matched by the 1st capturing group.

if i remove that how to re run
to see new output

so there is no submit button ..looks like site itself is running and giving output automatically