Identifiers Interview Questions and Answers

package training;
public class Employee {
    private int employeeId;
    public Employee(int employeeId) {
        // this.employeeId refers to the field.
        this.employeeId = employeeId;
    }
    public void displayEmployeeId() {
        System.out.println(employeeId);
    }
    public static void main(String[] args) {
        Employee employee = new Employee(101);
        employee.displayEmployeeId();
    }
}

public class IdentifierRules {
    public static void main(String[] args) {
        int employeeAge = 30;
        int _itemCount = 5;
        int total2 = 20;
        // int 2total = 20;     Invalid: starts with a digit.
        // int employee-age = 30; Invalid: contains a hyphen.
        // int class = 1;        Invalid: class is a keyword.
        System.out.println(employeeAge);
        System.out.println(_itemCount);
        System.out.println(total2);
    }
}

public class IdentifierCharacters {
    public static void main(String[] args) {
        int count = 10;
        int _total = 20;
        int $price = 30;
        int number2 = 40;
        // int 2number = 50; Invalid: a digit cannot be first.
        System.out.println(count + _total + $price + number2);
    }
}

public class SpecialIdentifiers {
    public static void main(String[] args) {
        int version2 = 21;
        int total_count = 50;
        int $generatedValue = 75;
        int संख्या = 100;
        // int _ = 10; Invalid: a single underscore is reserved.
        System.out.println(version2);
        System.out.println(total_count);
        System.out.println($generatedValue);
        System.out.println(संख्या);
    }
}

public class ReservedWordExample {
    public static void main(String[] args) {
        int classCount = 5;
        int returnValue = 10;
        // int class = 5; Invalid: class defines a Java declaration.
        // int return = 10; Invalid: return controls method execution.
        System.out.println(classCount + returnValue);
    }
}

public class CaseSensitiveExample {
    public static void main(String[] args) {
        int score = 10;
        int Score = 20;
        int SCORE = 30;
        // Java treats these as three different identifiers.
        System.out.println(score);
        System.out.println(Score);
        System.out.println(SCORE);
    }
}

public class IdentifierDifference {
    public static void main(String[] args) {
        // int is a keyword.
        // age is an identifier and variable name.
        // 25 is an integer literal.
        int age = 25;
        System.out.println(age);
    }
}

package com.example.payment;
public class PaymentService<T> {
    private static final int MAX_RETRY_COUNT = 3;
    private T paymentData;
    public PaymentService(T paymentData) {
        this.paymentData = paymentData;
    }
    public void displayPaymentData() {
        // Method and variable names use lowerCamelCase.
        System.out.println(paymentData);
        System.out.println(MAX_RETRY_COUNT);
    }
    public static void main(String[] args) {
        PaymentService<String> paymentService =
            new PaymentService<>("Payment completed");
        paymentService.displayPaymentData();
    }
}

public class SpecialIdentifierExample {
    public static void main(String[] args) {
        int var = 10;
        int _count = 20;
        // int true = 1; Invalid: true is a boolean literal.
        // int null = 2; Invalid: null is the null literal.
        // int _ = 3; Invalid as a normal named identifier.
        System.out.println(var);
        System.out.println(_count);
    }
}

public class Employee {
    private int employeeId;
    public Employee(int employeeId) {
        // The parameter shadows the instance field.
        this.employeeId = employeeId;
    }
    public void displayEmployeeId() {
        int employeeId = 500;
        // Uses the local variable.
        System.out.println(employeeId);
        // Uses the shadowed instance field.
        System.out.println(this.employeeId);
    }
    public static void main(String[] args) {
        Employee employee = new Employee(101);
        employee.displayEmployeeId();
    }
}

public class NamingExample {
    public static void main(String[] args) {
        // Valid but unclear identifiers.
        int x = 25;
        int $v = 5;
        // Valid and recommended identifiers.
        int employeeAge = 25;
        int retryCount = 5;
        System.out.println(x + $v);
        System.out.println(employeeAge + retryCount);
    }
}

public class UnicodeIdentifierExample {
    public static void main(String[] args) {
        int संख्या = 100;
        int किंमत = 50;
        // Unicode identifiers are valid Java identifiers.
        int एकूण = संख्या + किंमत;
        System.out.println(एकूण);
    }
}

public class IdentifierErrorExample {
    private int employeeId;
    // private int employeeId; Invalid: duplicate field.
    public void display(int count) {
        int total = 10;
        // int count = 5; Invalid: duplicates the parameter.
        // int total = 20; Invalid: duplicate local variable.
        // int 2value = 30; Invalid: begins with a digit.
        // int employee-name = 40; Invalid: contains a hyphen.
        System.out.println(count + total + employeeId);
    }
    public static void main(String[] args) {
        IdentifierErrorExample example = new IdentifierErrorExample();
        example.display(5);
    }
}

public class ProductService {
    private static final int MAX_RETRY_COUNT = 3;
    public double calculateDiscountedPrice(double productPrice) {
        // The name explains what the value represents.
        double discountRate = 0.10;
        return productPrice - productPrice * discountRate;
    }
    public static void main(String[] args) {
        ProductService productService = new ProductService();
        double finalPrice = productService.calculateDiscountedPrice(1000.0);
        System.out.println(finalPrice);
        System.out.println(MAX_RETRY_COUNT);
    }
}