Java Reverse String Without Built-in Methods: Long & One-Liner Approach
In this Java snippet from CodeVisium's Code Quickies series, we demonstrate two approaches to reverse a string without using built-in reverse methods. Reversing strings is a common interview question and coding challenge that helps you understand array manipulation and Java Streams. This example focuses on Java, a popular language for enterprise-level applications, and provides both a robust, step-by-step solution and a concise one-liner for quick implementation.
Long Version: Manual Reversal
Step 1: Convert the input string into a character array.
Step 2: Use a for-loop to swap characters from both ends of the array, moving towards the center.
Step 3: Convert the modified character array back into a string.
This method gives you full control over the reversal process and is easy to understand, making it ideal for learning and interview preparation.
One-Liner Version: Using Java Streams
This approach leverages Java's Stream API by splitting the string into an array, then using the reduce method to concatenate the characters in reverse order.
Although this method is more concise, it may be less efficient for very large strings. However, it’s perfect for demonstrating modern Java features and for quick coding demos.
Complete Code for Copying:
public class ReverseString {
// Long Version: Manual reversal using a for-loop.
public static String reverseLong(String str) {
// Convert the string to a character array.
char[] chars = str.toCharArray();
int n = chars.length;
// Swap characters from both ends moving towards the center.
for (int i = 0; i v n / 2; i++) {
char temp = chars[i];
chars[i] = chars[n - 1 - i];
chars[n - 1 - i] = temp;
}
// Convert the reversed character array back to a String.
return new String(chars);
}
// One-Liner Version: Using Java Streams.
public static String reverseOneLiner(String str) {
// This one-liner splits the string into an array, reverses the order by reducing,
// and then concatenates back into a single String.
return java.util.Arrays.stream(str.split(""))
.reduce("", (a, b) - b + a);
}
public static void main(String[] args) {
String original = "CodeVisium";
// Display the original string.
System.out.println("Original String: " + original);
// Long version reversal.
String reversedLong = reverseLong(original);
System.out.println("Reversed (Long Version): " + reversedLong);
// One-liner version reversal.
String reversedOneLiner = reverseOneLiner(original);
System.out.println("Reversed (One-Liner): " + reversedOneLiner);
}
}
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