String vs StringBuilder in Java - Hands-On Comparison

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String vs StringBuilder

📖 Scenario: Imagine you are writing a program that builds a message by adding words one by one. You want to see how using String and StringBuilder affects the way your program works.

🎯 Goal: You will create a simple Java program that first builds a message using String concatenation and then builds the same message using StringBuilder. You will see the difference in how the code looks and runs.

📋 What You'll Learn

Create a String variable with an initial value.

Create a StringBuilder variable with the same initial value.

Add words to both the String and the StringBuilder.

Print the final messages from both variables.

💡 Why This Matters

🌍 Real World

Building messages or text dynamically is common in apps like chat programs, reports, or logs.

💼 Career

Understanding when to use <code>String</code> or <code>StringBuilder</code> helps write efficient Java code, important for software developers.

1

Create a String variable

Create a String variable called message and set it to the value "Hello".

Java

# Create a String variable called message and set it to "Hello"
// Your code here

💡 Need a hint?

Use String message = "Hello"; to create the variable.

2

Create a StringBuilder variable

Add a StringBuilder variable called builder and set it to a new StringBuilder initialized with the value of message.

Java

public class Main {
    public static void main(String[] args) {
        String message = "Hello";
        // Create a StringBuilder variable called builder initialized with message
        // Your code here
    }
}

💡 Need a hint?

Use StringBuilder builder = new StringBuilder(message); to create the variable.

3

Add words to both variables

Add the word " World" to the message variable using + concatenation, and add the same word to the builder variable using the append() method.

Java

public class Main {
    public static void main(String[] args) {
        String message = "Hello";
        StringBuilder builder = new StringBuilder(message);
        // Add " World" to message using +
        // Add " World" to builder using append()
        // Your code here
    }
}

💡 Need a hint?

Use message = message + " World"; and builder.append(" World");.

4

Print both final messages

Print the message variable and then print the builder variable converted to a String using toString().

Java

public class Main {
    public static void main(String[] args) {
        String message = "Hello";
        StringBuilder builder = new StringBuilder(message);
        message = message + " World";
        builder.append(" World");
        // Print message
        // Print builder as String
        // Your code here
    }
}

💡 Need a hint?

Use System.out.println(message); and System.out.println(builder.toString());.