A lightweight, zero-dependency Java library for clean and semantically correct argument validation.

When validating method and constructor arguments, Args provides a better alternative to Objects.requireNonNull() with three key advantages:

Throws IllegalArgumentException (indicating invalid input) rather than NullPointerException (indicating a programming bug). This distinction is crucial for proper exception handling and debugging.

Returns the validated value, enabling clean inline validation that's especially elegant in Java record compact constructors:

public record User(UUID id, String name) {
  public User {
    Args.notNull(id, "ID cannot be null");
    Args.notBlank(name, "Name cannot be blank");
  }
}

Provides a uniform validation API for common scenarios:

• Null checks: notNull()
• Empty checks: notEmpty() for arrays and strings
• Blank checks: notBlank() for strings
• Boolean conditions: requireTrue() and requireFalse()

dependencies {
    implementation("io.github.appcomponents:args:VERSION")
}

dependencies {
    implementation 'io.github.appcomponents:args:VERSION'
}

<dependency>
    <groupId>io.github.appcomponents</groupId>
    <artifactId>args</artifactId>
    <version>VERSION</version>
</dependency>

public void processUser(User user) {
    Args.notNull(user, "User cannot be null");
    // ... process user
}

// With default message
String value = Args.notNull(parameter);

// Ensure string is not null or empty
String username = Args.notEmpty(input, "Username cannot be empty");

// Ensure string is not null or blank (all whitespace)
String password = Args.notBlank(input, "Password cannot be blank");

// Works with all primitive and object arrays
byte[] data = Args.notEmpty(bytes, "Data cannot be empty");
int[] numbers = Args.notEmpty(values, "Values cannot be empty");
String[] names = Args.notEmpty(items, "Items cannot be empty");

// Validate arbitrary conditions
Args.requireTrue(age >= 18, "User must be 18 or older");
Args.requireFalse(isBlocked, "User account is blocked");

The return-value design makes Args particularly elegant for Java records:

public record Product(
    UUID id,
    String name,
    BigDecimal price,
    String[] tags
) {
  public Product {
    id = Args.notNull(id, "Product ID is required");
    name = Args.notBlank(name, "Product name is required");
    price = Args.notNull(price, "Price is required");
    tags = Args.notEmpty(tags, "At least one tag is required");

    Args.requireTrue(price.compareTo(BigDecimal.ZERO) > 0,
                     "Price must be positive");
  }
}

• <T> T notNull(T object) - Validates object is not null
• <T> T notNull(T object, String message) - Validates with custom message

• String notEmpty(String string) - Validates string is not null or empty
• String notEmpty(String string, String message) - Validates with custom message
• String notBlank(String string) - Validates string is not null or blank
• String notBlank(String string, String message) - Validates with custom message

All primitive types and Object[] are supported:

• byte[] notEmpty(byte[] array)
• char[] notEmpty(char[] array)
• short[] notEmpty(short[] array)
• int[] notEmpty(int[] array)
• long[] notEmpty(long[] array)
• float[] notEmpty(float[] array)
• double[] notEmpty(double[] array)
• boolean[] notEmpty(boolean[] array)
• Object[] notEmpty(Object[] array)

Each array method has a variant accepting a custom message.

• void requireTrue(boolean condition, String message) - Throws if condition is false
• void requireFalse(boolean condition, String message) - Throws if condition is true

Use Args for validating method and constructor parameters where invalid input is a client error.

Use Objects.requireNonNull() for internal null-checks where NullPointerException is semantically appropriate (indicating a programming bug).

All Args methods throw IllegalArgumentException to indicate that the caller provided invalid arguments.

• Java 17 or higher
• Zero dependencies (except test dependencies)

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.

Contributions are welcome! Please feel free to submit a Pull Request.

If you encounter any issues or have questions, please file an issue on the GitHub issue tracker.