Learn what the String Constant Pool is in Java, how it optimizes memory, and why String literals are stored differently than objects. Includes code examples and explanations.

Ramesh Fadatare

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Mar 25, 2025

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Introduction

If you’re learning Java, you’ve probably used String values like this:

String name = "Ramesh";

But did you know this string is stored differently than using new String("Ramesh")?

This is because of something called the String Constant Pool.

In this article, we’ll explore:

• What the String Constant Pool is
• Why Java uses it
• How it improves memory usage
• Key examples and interview tips

📌 What is the String Constant Pool?

In Java, the String Constant Pool (also called the String Intern Pool) is a special memory area in the Java Heap that stores string literals.

✅ Simply put:

It’s a memory optimization technique that avoids creating duplicate String objects with the same value.

🔍 How It Works

When you create a string like this:

String str1 = "Java";

➡️ Java stores "Java" in the String Pool. If you later write:

String str2 = "Java";

➡️ Java doesn’t create a new object — it simply points str2 to the same "Java" instance in the pool.

But if you do:

String str3 = new String("Java");

➡️ It creates a new object in the heap, even if "Java" already exists in the pool.

✅ Why Does Java Do This?

• Strings are immutable, meaning they can’t be changed once created.
• Many programs use the same string values repeatedly (like "yes", "no", "OK").
• So instead of creating multiple "yes" strings, Java reuses the same one in the pool, saving memory.

🔄 String Pool vs. Heap

💡 Code Example: String Pool in Action