Java @SafeVarargs Annotation

Introduction

The @SafeVarargs annotation in Java is used to suppress warnings related to varargs when the method does not perform potentially unsafe operations on the varargs parameter.

Table of Contents

1. What is @SafeVarargs?
2. When to Use @SafeVarargs
3. Examples
4. Conclusion

1. What is @SafeVarargs?

@SafeVarargs is an annotation used to indicate that a method with a variable number of arguments (varargs) is safe from heap pollution. It is applicable to methods or constructors that are final, static, or private.

2. When to Use @SafeVarargs

• When you have a method or constructor that accepts varargs and does not perform unsafe operations, like storing the varargs in a field or modifying them.
• Applicable to final, static, or private methods and constructors.

3. Examples

Example 1: Using @SafeVarargs in a Static Method

This example demonstrates the use of @SafeVarargs in a static method.

import java.util.List;

public class SafeVarargsExample {
    @SafeVarargs
    public static <T> void printElements(T... elements) {
        for (T element : elements) {
            System.out.println(element);
        }
    }

    public static void main(String[] args) {
        printElements("One", "Two", "Three");
        printElements(1, 2, 3, 4, 5);
    }
}

Output:

One
Two
Three
1
2
3
4
5

Example 2: Using @SafeVarargs in a Final Method

This example shows @SafeVarargs in a final method.

public class FinalMethodExample {
    @SafeVarargs
    public final <T> void display(T... values) {
        for (T value : values) {
            System.out.println(value);
        }
    }

    public static void main(String[] args) {
        FinalMethodExample example = new FinalMethodExample();
        example.display("A", "B", "C");
        example.display(10, 20, 30);
    }
}

Output:

A
B
C
10
20
30

4. Conclusion

The @SafeVarargs annotation in Java helps suppress warnings for safe varargs usage, improving code readability and preventing unnecessary warnings. It should be used carefully, ensuring that the method or constructor does not perform unsafe operations on the varargs parameters.