How to Optimize String Creation in Java?

Last Updated : 02 Dec, 2024

In Java, strings are frequently used, and optimizing their creation can help improve performance, especially when creating many strings in a program. In this article, we will explore simple ways to optimize string creation in Java.

Example:

Using the new keyword creates a new string object. This is straightforward but can be slow if used repeatedly.

Java

// String creation using new keyword
public class StringCreation {
  
    public static void main(String[] args) {
      
        String[] s = new String[50000];       // Array of strings
        long startTime = System.currentTimeMillis();

        for (int i = 0; i < 50000; i++) {
          
            // Using 'new' to create strings
            s[i] = new String("GeeksforGeeks");  
        }

        long endTime = System.currentTimeMillis();
        System.out.println("Time taken using 'new': " 
                           + (endTime - startTime) + " ms");
    }
}

Output

Time taken using 'new': 5 ms

Different Ways to Optimize String Creation in Java

1. Using `String.intern()` Method

String.intern() method helps by storing only one copy of each string in memory. This is useful if the same string is used multiple times in your program.

Java

// String creation using intern() method
public class StringCreation {
  
    public static void main(String[] args) {
      
        String[] s = new String[50000];     // Array of strings
        long startTime = System.currentTimeMillis();

        for (int i = 0; i < 50000; i++) {
          
            // Interning the string
            s[i] = new String("GeeksforGeeks").intern();   
        }

        long endTime = System.currentTimeMillis();
        System.out.println("Time taken using intern(): " 
                           + (endTime - startTime) + " ms");
    }
}

Output

Time taken using intern(): 43 ms

Note: The creation time of objects with an intern() and creation time of objects with 'new' keyword fluctuate near each other's creation time.

2. Using String Literals

A string literal is the most efficient way to create strings. When you use a string literal, Java automatically checks if the string already exists in the memory and reuses it.

Note: It is the fastest way of string creation.

Example:

Java

// String creation using literals
public class StringCreation {
  
    public static void main(String[] args) {
      
        String[] s = new String[50000];      // Array of strings
        long startTime = System.currentTimeMillis();

        for (int i = 0; i < 50000; i++) {
          
            // Using a string literal
            s[i] = "GeeksforGeeks";  
        }

        long endTime = System.currentTimeMillis();
        System.out.println("Time taken using string literals: " 
                           + (endTime - startTime) + " ms");
    }
}

Output

Time taken using string literals: 2 ms