Different Way to Find Matching Substring From a String Java Program?

package com.softwaretestingblog.InterviewPgms;
import java.util.Scanner;
public class StringIndexof 
{
   public static void main(String[] args) 
   {
      String str="abababababaabb";
      String sub = "bab";

      int n = str.length();
      int m = sub.length();

      // index=-1 in case of no match, otherwise >=0(first match position)
      int index=str.indexOf(sub), i=index+1, count=(index>=0)?1:0;
      //System.out.println(i+" "+index+" "+count);

      // i will traverse up to only (m-n) position
      while(index!=-1 && i<=(n-m))
      {   
         index=str.substring(i, n).indexOf(sub);
         count=(index>=0)?count+1:count;
         i=i+index+1;  
         //System.out.println(i+" "+index);
      }
      System.out.println("Total Number Of Substring Appears: "+count);
   }
}

Find Matching Substring Output:

Total Number Of Substring Appears: 4

Solution 2:

Here is the advanced version for counting how many times the token occurred in a user entered the string.

package com.softwaretestingblog.InterviewPgms;
import java.util.Scanner;
public class StringIndexof 
{
   public static void main(String[] args) 
   {
      Scanner scanner = new Scanner(System.in);

        System.out.println("Enter a sentence please:");
        String string = scanner.nextLine();

        int atIndex = 0;
        int count = 0;

        while (atIndex != -1)
        {
            atIndex = string.indexOf("hello", atIndex);

            if(atIndex != -1)
            {
                count++;
                atIndex += 5;
            }
        }
      System.out.println("Total Number Of Hello Substring Appears: "+count);
   }
}

Find Matching Substring Output:

Enter a sentence please:
helloslkhellodjladfjhelloarunkumarhelloasdhelloaruhelloasrhello
Total Number Of Hello Substring Appears: 7

Solution 3:

package com.softwaretestingblog.InterviewPgms;
public class StringIndexof 
{
   public static void main(String[] args) 
   {
      String str = "helloslkhellodjladfjhello";
      String findStr = "hello";

      int count = 0, lastIndex = 0;
      while((lastIndex = str.indexOf(findStr, lastIndex)) != -1) {
          lastIndex += findStr.length() - 1;
          count++;
      }
      
      System.out.println("Total Number Of Hello Substring Appears: "+count);
   }
}

Find Matching Substring Output:

Total Number Of Hello Substring Appears: 3

Solution 4:

Find The Number of Times Substring Appear In String By RegularExpression

• Patterns of arbitrary length
• Overlapping matches (such as counting “232” in “23232” or “aa” in “aaa”)
• Regular expression meta-characters

package com.softwaretestingblog.InterviewPgms;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class StringIndexof 
{
   static int countMatches(Pattern pattern, String string)
   {
       Matcher matcher = pattern.matcher(string);

       int count = 0;
       int pos = 0;
       while (matcher.find(pos))
       {
           count++;
           pos = matcher.start() + 1;
       }

       return count;
   }
   public static void main(String[] args) 
   {
      Pattern pattern = Pattern.compile("232");
      int count = countMatches(pattern, "23232");
      System.out.println("No Of Times Sub String Appears:-"+count);
   }
}

Find Matching Substring Output:

No Of Times Sub String Appears:-2

Solution 5:

package com.softwaretestingblog.InterviewPgms;
public class StringIndexof 
{
   public static void main(String[] args) 
   {
      String str = "helloslkhellodjladfjhello";
      String findStr = "hello";
      int lastIndex = 0;
      int count = 0;

      while((lastIndex = str.indexOf(findStr, lastIndex)) != -1) {
           count++;
           lastIndex += findStr.length() - 1;
      }
      System.out.println("Total Number Of Substring :-"+count);
   }
}

Output:

Total Number Of Substring :-3

Solution 6:

package com.softwaretestingblog.InterviewPgms;
public class StringIndexof 
{
   public  static  int getCountSubString(String str , String sub){
      int n = 0, m = 0, counter = 0, counterSub = 0;
      while(n < str.length()){
         counter = 0;
         m = 0;
         while(m < sub.length() && str.charAt(n) == sub.charAt(m)){
            counter++;
            m++; n++;
         }
         if (counter == sub.length()){
            counterSub++;
            continue;
         }
         else if(counter > 0){
            continue;
         }
         n++;
      }

      return  counterSub;
   }
   public static void main(String[] args) 
   {
      int count;
      String str = "helloslkhellodjladfjhelloarunkumarhelloasdhelloaruhelloasrhello";
        String findStr = "hello";
      StringIndexof obj=new StringIndexof();
      count=obj.getCountSubString(str, findStr);
      System.out.println("Total Number Of Substring :-"+count);
   }
}

Output:

Total Number Of Substring :-7

Solution 7:

here is the other solution without using regexp/patterns/matches or even not using StringUtils.

package com.softwaretestingblog.InterviewPgms;
public class StringIndexof 
{
   public static void main(String[] args) 
   {
      String str = "helloslkhellodjladfjhelloarunkumarhelloasdhelloaruhelloasrhello";
        String findStr = "hello";
        int count =0;
        int findStrLength = findStr.length();
        for(int i=0;i<str.length();i++){
            if(findStr.startsWith(Character.toString(str.charAt(i)))){
                if(str.substring(i).length() &gt;= findStrLength){
                    if(str.substring(i, i+findStrLength).equals(findStr)){
                        count++;
                    }
                }
            }
        }
      System.out.println("Total Number Of Substring :-"+count);
   }
}

Output:

Total Number Of Substring :-7

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