Java Interview Questions SET-01

Java Interview Questions Set-02 ARRAY

Java Interview Questions Set-03 MAP

Java Interview Question Set-04

What are Java Generics?

Java generics provide a way to create classes, interfaces, and methods that can work with different types of objects. Generics allow you to specify placeholder types, called type parameters, which are replaced with actual types when the code is used.

Java generics are like special boxes that can hold different types of things.
Just like you have different boxes for toys, books, and clothes, Java generics allow us to create boxes that can hold different types of data.
Java generics provide type safety and enable code reusability by allowing classes, interfaces, and methods to work with different types of objects.
Generics eliminate the need for type casting and ensure compile-time type checking.
They are widely used in collections to enforce type constraints and provide compile-time type safety.
Bounded type parameters in generics allow for restricting acceptable types, enhancing flexibility in type handling.
Java generics enhance code readability and maintainability by promoting cleaner and more concise code.

Why do we use Java Generics?

Imagine you have a magic box that can hold any kind of toy: cars, dolls, or action figures.
Java generics work similarly. They allow us to create code that can work with different types of data without duplicating the code.

What are the different ways to call a method in Java? <- Must Know

How to use Java Generics?

Let's say we want to create a box that can hold any kind of toy. We use the angle brackets "<>" to create a generic class or method.

Example: Creating a generic class

\
public class ToyBox<T> {
    private T toy;

    public T getToy() {
        return toy;
    }

    public void setToy(T toy) {
        this.toy = toy;
    }
}

Here, "T" is a placeholder for any type of toy. It could be a Car, Doll, or any other toy.

Example: Using the generic class

ToyBox<Car> carBox = new ToyBox<>();
carBox.setToy(new Car());
Car car = carBox.getToy();

ToyBox<Doll> dollBox = new ToyBox<>();
dollBox.setToy(new Doll());
Doll doll = dollBox.getToy();

We can create different toy boxes, such as a car box or a doll box, and put specific types of toys in them.

Benefits of Java Generics:

Code reusability:
We can write generic code that can work with different types of data without duplicating the code.
Type safety:
Generics provide compile-time checks to ensure that we are using the correct types, reducing errors and bugs.

Array vs List vs MAP <- refer the link here

Key points:

Java generics are like special boxes that can hold different types of things.
Generics help us write code that can work with different types of data without duplicating code.
We use angle brackets "<>" to create generic classes or methods.
Generics provide code reusability and type safety.

Learn about Java Coding Standards [Imp for SDET ad Automation QA]

Java Generics in Test Automation

Here's an example of how you can use generics to create a generic assertion method for comparing two lists of any type:

import java.util.List;

public class AssertionUtils {
public static <T> void assertListsEqual(List<T> expected, List<T> actual) {
if (expected.size() != actual.size()) {
throw new AssertionError("Lists are not of the same size");
}

for (int i = 0; i < expected.size(); i++) {
if (!expected.get(i).equals(actual.get(i))) {
throw new AssertionError("Lists differ at index " + i +
"\nExpected: " + expected.get(i) +
"\nActual: " + actual.get(i));
}
}
}
}

In this example, we have a class called AssertionUtils that contains a generic method called assertListsEqual(). This method takes two parameters: expected and actual, which are both lists of type T.

The <T> before the return type void represents the generic type parameter. It allows the method to work with any type of list.

Inside the method, we first check if the sizes of the expected and actual lists are equal. If they are not, we throw an AssertionError indicating that the lists are not of the same size.

Then, we iterate over the elements of both lists and compare them using the equals() method. If any pair of elements differs, we throw an AssertionError indicating the index at which the lists differ, along with the expected and actual values.

How to use Java ENUM in Test Automation Framework

Here's an example usage of the assertListsEqual() method:

import java.util.Arrays;
import java.util.List;
public class TestAssertions {
public static void main(String[] args) {
List<String> expected = Arrays.asList("apple", "banana", "orange");
List<String> actual = Arrays.asList("apple", "grape", "orange");
AssertionUtils.assertListsEqual(expected, actual);
}
}

In this example, we have two lists: expected and actual. We call the assertListsEqual() method from AssertionUtils and pass the lists as arguments. If the lists are not equal, an AssertionError will be thrown with the appropriate message indicating the index and the expected/actual values.

By using generics in this way, you can create a single generic assertion method that can compare two lists of any type, making your test assertions more reusable and flexible.

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