What's the Most Efficient Way to Convert Integers to Strings in Java?

Converting Integers to Strings in Java: Best Practices

When working with Java, converting integers to strings is a common task. While the following code snippet demonstrates a simple approach to this conversion:

int i = 5;
String strI = "" + i;

this method is considered unconventional and raises questions about the developer's knowledge of Java's more efficient conversion methods:

• Integer.toString(i): This method directly converts an integer to a string.
• String.valueOf(i): This method also converts an integer to a string.

Although string concatenation using the operator is valid in Java, it is less efficient and unconventional, suggesting that the developer may not be aware of the more appropriate methods.

Furthermore, the Java compiler does not optimize out the empty string in this scenario, resulting in an additional overhead. To illustrate this, consider the following class:

public class TestClass {
  public static void main(String[] args) {
    int i = 5;
    String strI = "" + i;
  }
}

Compiling and disassembling this class using javac and javap -c reveals that the compiler initializes a StringBuilder, appends an empty string, appends the integer, and extracts the final string.

While this method works, it is less efficient than the dedicated conversion methods. To address this, a proposal is underway to change this behavior in JDK 9.

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