public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}
Ask the right questions to secure the right Java talent among an increasingly shrinking pool of talent.
Java, a high-level computer programming language, was developed by Sun Microsystems in 1995, now owned by Oracle Corporation. It is an object-oriented language, designed to be simple and secure, and is used for developing platform-independent web and mobile applications. Java's "Write Once, Run Anywhere" principle ensures compatibility across different operating systems. Its syntax is derived from C and C++, making it familiar to many programmers. Today, Java is widely used in enterprise-scale applications, Android app development, and Internet of Things (IoT) technology.
The next 20 minutes of the interview should attempt to focus more specifically on the development questions used, and the level of depth and skill the engineer possesses.
Annotations are a form of metadata that provide data about a program that is not part of the program itself. They have no direct effect on the operation of the code they annotate. Annotations can be read from source files, class files, or reflectively at runtime.
In Java, exceptions are handled using a try-catch block. We can also use a finally block to ensure that a certain section of code runs regardless of whether an exception is thrown or not.
An abstract class can have method implementations, but an interface can't. All methods of an Interface are implicitly abstract and public. An abstract class can have both abstract and non-abstract methods. An interface can have variables, but they're implicitly final and static.
Java Class Loaders are part of the Java Runtime Environment that dynamically loads Java classes into the JVM. They are used to load classes and interfaces. There are three built-in class loaders in Java: Bootstrap ClassLoader, Extensions ClassLoader and System ClassLoader.
The main principles of OOP in Java are encapsulation, inheritance, polymorphism, and abstraction. Encapsulation is the mechanism of hiding data implementation by wrapping data and functions into a single unit. Inheritance is a mechanism where an object acquires all the properties and behaviors of a parent object. Polymorphism allows an object to take on many forms. Abstraction is a process of hiding the implementation details and showing only functionality.
Good communication skills are essential for a developer. The candidate should be able to explain their thought process, discuss problems and solutions, and work well in a team.
Most applications involve some form of data storage and retrieval. The candidate should have experience working with SQL databases and possibly NoSQL databases.
Problem-solving skills are critical for any developer. The candidate should be able to demonstrate their ability to solve complex problems using Java.
A good Java developer should be familiar with tools and technologies that are commonly used in the Java ecosystem, such as Maven, Jenkins, and Spring Framework.
Java is an object-oriented programming language. The candidate should have a solid understanding of concepts such as inheritance, polymorphism, encapsulation, and abstraction.
A strong foundation in Java is crucial for a Java developer position. This includes knowledge of data types, variables, loops, and control structures.
The next 20 minutes of the interview should attempt to focus more specifically on the development questions used, and the level of depth and skill the engineer possesses.
HashMap is a general purpose Map implementation. It provides a performance of O(1) for get() and put() operations. TreeMap is a sorted map implementation. It provides a performance of O(log(n)) for get() and put() operations. HashMap does not maintain any order, whereas TreeMap maintains elements in sorted order.
The sleep() method is a static method that pauses the execution of the current thread for a specified time. The wait() method is used in synchronization for inter-thread communication and it releases the lock while waiting.
There are two ways to create a thread in Java - by extending the Thread class and by implementing the Runnable interface. After creating a thread, the start() method is used to make the thread eligible for running.
Java Generics add a layer of abstraction over types, allowing code to be written in a generic manner, reducing bugs and adding an extra layer of security. They were added to provide compile-time type checking and removing risk of ClassCastException that was common while working with collection classes.
Checked exceptions are checked at compile-time, while unchecked exceptions are checked at runtime. Checked exceptions need to be declared in a method or constructor's throws clause if they can be thrown by the execution of the method or constructor and propagate outside the method or constructor boundary.
At this stage, a skilled Java engineer should demonstrate strong proficiency in Java and related frameworks, an understanding of object-oriented programming principles, and problem-solving capabilities. Red flags include inability to explain concepts clearly, lack of practical experience, and poor code optimization techniques.
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}
public final class Test {
public void show() {
System.out.println("This is a final class.");
}
}
import java.util.Arrays;
public class Test {
public static void main(String[] args) {
int[] array = {1, 2, 3, 4, 5};
Arrays.sort(array);
System.out.println(Arrays.toString(array));
}
}
public class Test extends Thread {
public void run() {
System.out.println("Thread is running.");
}
public static void main(String[] args) {
Test t = new Test();
t.start();
}
}
public class Test {
private int x;
public Test(int x) {
this.x = x;
}
public int getX() {
return x;
}
}
public class Test {
public static void main(String[] args) {
try {
int x = 5 / 0;
} catch (ArithmeticException e) {
System.out.println("Arithmetic Exception");
} finally {
System.out.println("Finally block executed");
}
}
}
The final few interview questions for a Java candidate should typically focus on a combination of technical skills, personal goals, growth potential, team dynamics, and company culture.
Deadlock can be prevented by a number of ways such as: avoiding nested locks, avoiding unnecessary locks, using thread join to ensure a thread doesn't proceed until another finishes, or using a deadlock detection algorithm.
A Set in Java is a collection which cannot contain duplicate elements. It models the mathematical set abstraction. A List is an ordered collection and can contain duplicate elements. You can access any element from its index. List is more like array with dynamic length.
In Java, memory management is mostly handled by the Garbage Collector. However, we can assist the Garbage Collector by making sure we dereference objects that are no longer needed, and by using the 'finalize' method to free up other non-Java resources.
The == operator checks if the two references point to the exact same object, whereas the equals() method checks if the two objects are logically equivalent, according to the implementation of equals() in their class.
In Java, SQL Injection can be prevented by using Prepared Statements and Callable Statements. They work by precompiling the SQL statement which means special characters do not have any meaning and cannot change the intent of the SQL statement.
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