Java String Length: How to Find it Without the length() Method

You can find the length of a string without using Java's built-in length() method by iterating through the characters of the string and counting them manually. Here's a simple example using a loop to achieve this:

Example-1:

In this example, the getStringLength method takes a string as input and iterates through its characters using a for-each loop. It increments the count variable for each character encountered. The final value of count will be the length of the input string, and that's what is returned by the method.

Keep in mind that this is just an alternative way to find the length of a string and not as efficient as using the built-in length() method, which is optimized for performance. Example-2:

In this approach, the getStringLength method uses recursion to find the length of the string. The base case checks if the input string is empty, in which case the length is 0. In the recursive case, the method calls itself with the substring starting from the second character (str.substring(1)), and then adds 1 to the result to account for the first character. 

Again, while this method demonstrates an alternative approach, it is generally less efficient and less readable than using the built-in length() method. Recursion can be less performant for very long strings due to the overhead of method calls. The built-in length() method is the preferred way to get the length of a string in Java. 

Example-3:

In this example, the getStringLength method iterates through the string using a while loop and the charAt() method. It starts with index = 0 and tries to access the character at that index. If the index is within the valid range of the string, it increments the length variable and moves to the next character by incrementing the index. The loop continues until it encounters a StringIndexOutOfBoundsException, indicating that the index is out of bounds, and hence the end of the string has been reached. 

Please note that this method is not as efficient as using the built-in length() method, especially for long strings, because it involves repeatedly accessing characters one by one. It's generally better to use the built-in length() method for most scenarios. 

Output:

Length of the string: 13

• Using a Loop:

        Advantages:

• Simple and easy-to-understand code.

• No additional memory overhead, as it doesn't create new objects or strings.

• Works efficiently for most strings and lengths.

        Disadvantages:

• Slightly less efficient compared to the built-in length() method because of the manual  iteration.

• The length calculation takes linear time with respect to the length of the string, so very long strings might take more time.

• Using Recursion: 

• Demonstrates the concept of recursion and its application to find the length of a string.

• No additional memory overhead apart from the method call stack.

• Works for most strings and lengths.

        Disadvantages:

• Less efficient compared to both the built-in length() method and the loop method, due to repeated method calls and stack usage.

• Could lead to a StackOverflowError for very long strings due to excessive recursion.

• Using charAt() with While Loop:

        Advantages:

• Simple code that directly accesses the characters of the string without creating new objects or strings.

• Works for most strings and lengths.

        Disadvantages:

• Less efficient compared to the built-in length() method, as it involves repeated checks for index out of bounds.

• It takes linear time with respect to the length of the string, so very long strings might take more time.

• The code is not as concise as the loop method.

Summary:

• All three methods are valid ways to find the length of a string without using length(), and they will give you correct results for most scenarios.

• If efficiency is crucial, the built-in length() method is the most optimal choice.

• If you're looking for simplicity and readability, the loop method is the most straightforward.

• Recursion can be an interesting alternative for educational purposes, but it is generally less efficient and may have limitations for very long strings.

• The charAt() with the while loop method is a bit more verbose and slightly less efficient than the loop method.

Choose the method that best fits your specific use case and prioritize readability, maintainability, and efficiency based on the context in which you're working.