CountVowels()

Step 1: Problem Understanding

In this task, we are going to create a function in Java that will count the number of vowels in a given string. This function can be very helpful when you are dealing with string manipulation or string related problem.

public class Main  {

}

Step 2: Declare the Method

Firstly, we create a public method named 'countVowels', which accepts a string and returns the count of vowels. For now, our function returns zero as we have not implemented the logic yet.

public class Main  {
 public static int countVowels(String str) {
  return 0;
 }
}

Step 3: Implement the Logic

Now, we are going to implement our logic to count the vowels. We will traverse through each character of the string, and check if it is a vowel. If yes, we will increase our count.

public class Main  {
 public static int countVowels(String str) {
  int count = 0;
  for (int i = 0; i < str.length(); i++) {
   char ch = str.charAt(i);
   if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
    count++;
   }
  }
  return count;
 }
}

Step 4: Making the Function Case Insensitive

The above function will only count lowercase vowels. However, vowels can be uppercase as well. So, we need to modify our function to handle this case. For this, we will convert our string to all lower case and then apply the logic.

public class Main  {
 public static int countVowels(String str) {
  int count = 0;
  str = str.toLowerCase();
  for (int i = 0; i < str.length(); i++) {
   char ch = str.charAt(i);
   if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
    count++;
   }
  }
  return count;
 }
}

Conclusion

We have successfully created a function in Java that can count the number of vowels in a given string. It is easy to understand and efficient. Always remember, string manipulation tasks are very common in programming and having a good grip on it will help you with coding interviews and problem-solving.

Here is the final code:

public class Main  {
 public static int countVowels(String str) {
  int count = 0;
  str = str.toLowerCase();
  for (int i = 0; i < str.length(); i++) {
   char ch = str.charAt(i);
   if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
    count++;
   }
  }
  return count;
 }
}