Test in JUNIT

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;

public class CalculatorTest {

private final Calculator calculator = new Calculator();

@Test void testAdd() { assertEquals(5, calculator.add(2, 3), "2 + 3 should equal 5"); assertEquals(0, calculator.add(0, 0), "0 + 0 should equal 0"); assertEquals(-1, calculator.add(2, -3), "2 + -3 should equal -1"); }

@Test void testSubtract() { assertEquals(-1, calculator.subtract(2, 3), "2 - 3 should equal -1"); assertEquals(0, calculator.subtract(3, 3), "3 - 3 should equal 0"); assertEquals(5, calculator.subtract(2, -3), "2 - -3 should equal 5"); }

}

Annotation in Java

In Java, annotations are a form of metadata that provide data about a program but are not part of the program itself. They can be used for various purposes, such as providing information to the compiler, generating code, or affecting the runtime behavior of applications.

Common Annotations in Java

1. @Override:
   • Indicates that a method is overriding a method from a superclass.
   • Helps in ensuring that the method signature matches the method in the superclass.
2. @Deprecated:

• Marks a method, class, or field as deprecated, indicating that it should no longer be used.
• The compiler generates a warning if the deprecated element is used.

1. @SuppressWarnings:

• Instructs the compiler to suppress specific warnings.
• Commonly used to suppress unchecked or deprecation warnings.

1. @FunctionalInterface:

• Indicates that an interface is intended to be a functional interface (i.e., it has exactly one abstract method).
• Useful for lambda expressions and method references.

1. @Retention:

• Specifies how long annotations with the annotated type are to be retained.
• Can have three values: SOURCE, CLASS, or RUNTIME.

java
Copy code
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
    // Annotation elements
}

Custom Annotations