Replace First Character Of String

When working with strings in programming, you may come across situations where you need to replace the first character of a string with another character. This task might seem simple but can be crucial in certain scenarios. In this article, we will guide you through the process of replacing the first character of a string in various programming languages.

Python:

In Python, strings are immutable, which means you cannot modify them directly. To replace the first character of a string, you can create a new string by concatenating the new character with the rest of the original string. Here's an example code snippet:

Python

def replace_first_char(input_str, new_char):
    return new_char + input_str[1:]

# Test the function
original_str = "hello"
new_str = replace_first_char(original_str, "H")
print(new_str)  # Output: "Hello"

In this Python function, `replace_first_char`, we take the input string and the new character as arguments. We then return a new string by combining the new character with the substring starting from the second character of the original string.

JavaScript:

Similarly, in JavaScript, strings are immutable. We can achieve the task of replacing the first character of a string by using the `substr` method along with string concatenation. Here's how you can do it:

Javascript

function replaceFirstChar(inputStr, newChar) {
    return newChar + inputStr.substr(1);
}

// Test the function
let originalStr = "hello";
let newStr = replaceFirstChar(originalStr, "H");
console.log(newStr);  // Output: "Hello"

In this JavaScript function `replaceFirstChar`, we use the `substr` method to extract the substring starting from the second character of the original string and then concatenate it with the new character.

Java:

In Java, strings are immutable too. To replace the first character of a string, we can create a new string using the `substring` method. Here's a Java example:

Java

public static String replaceFirstChar(String inputStr, char newChar) {
    return newChar + inputStr.substring(1);
}

// Test the function
String originalStr = "hello";
String newStr = replaceFirstChar(originalStr, 'H');
System.out.println(newStr);  // Output: "Hello"

In this Java method `replaceFirstChar`, we use the `substring` method to extract the substring starting from the second character of the original string, and then we concatenate it with the new character to create the updated string.

By following these examples in Python, JavaScript, and Java, you can easily replace the first character of a string in your code. Remember to consider the immutability of strings in your programming language when performing such tasks.

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