Top 50 Java Programming Interview Questions

The interface is implemented by class thereby, inheriting the abstract methods of the interface. Exception handling is a mechanism to handle runtime errors. We perform exception handling to maintain the normal flow of the application.

What is the difference between the ‘throw’ and ‘throws’ keyword in Java?

Preparing for a Core Java interview requires practice, dedication, and a solid understanding of Core Java concepts and programming skills. By following the above tips, you can escalate your chances of acing the interview and landing your dream Java job. A stream filter, also called a filter stream, returns a stream composed of the stream’s items that satisfy the given predicate. ByteStream classes and CharacterStream classes are the two categories into which all stream classes can be separated. Bytes support a minimum of -128 and a maximum of 127 values.

Write Java program that checks if two arrays contain the same elements.

It is a type of run-time exception that is thrown when the program attempts to use an object reference that has a null value. The main use of NullPointerException is to indicate that no value is assigned to a reference variable, also it is used for implementing data structures like linked lists and trees. The static keyword is used to share the same variable or method of a given class. Static variables are the variables that once declared then a single copy of the variable is created and shared among all objects at the class level. In Java, a class variable (also known as a static variable) is a variable that is declared within a class but outside of any method, constructor, or block.

What is the final variable?

Java package is the mechanism to organize the java classes by grouping them. The grouping logic can be based on functionality or modules based. A java class fully classified name contains package and class name. For example, java.lang.Object is the java interview questions for senior developer fully classified name of Object class that is part of java.lang package. The overriding concept comes into the picture with inheritance when we have two methods with the same signature, one in the parent class and another in the child class.

In the below Java Program, how many objects are eligible for garbage collection?

No, this cannot be assigned to any value because it always points to the current class object and this is the final reference in Java. However, if we try to do so, the compiler error will be shown. Here, the data type of the variables a and b, i.e., byte gets promoted to int, and the first parameterized constructor with the two integer parameters is called. The local variables are not initialized to any default value, neither primitives nor object references.

How is the creation of a String using new() different from that of a literal? When we create a string using new(), a new object is created. Whereas, if we create a string using the string literal syntax, it may return an already existing object with the same name. ClassLoader is a subset of Java Virtual Machine (JVM), and it loads class files. When a Java program gets executed, the ClassLoader is what loads it.

What do you understand by copy constructor in Java?

1. When we are working with the files or stream then to increase the Input/Output performance of the program we need to use the BufferedInputStream and BufferedOutputStream classes.
2. Therefore we use collection where heterogenous or dissimilar objects can be stored.
3. An infinite loop will terminate automatically once the application exits.
4. In some cases, multiple methods have the same name, but different formal argument lists (overloaded methods).
5. Reflection API usage can break the design pattern such as Singleton pattern by invoking the private constructor i.e violating the rules of access modifiers.

Yes, there is a possibility that the ‘finally’ block cannot get executed. Here are some of the cases where the above situation occurs. One approach to not allow serialization of attributes of a class in Java is by using writeObject() and readObject() methods in the subclass and throwing a not Serializable exception. The throw keyword is often used to explicitly throw an exception. It can only throw one exception at a time whereas throws can be used to declare multiple exceptions.

An anonymous class is a class defined without any name in a single line of code using new keyword. If a class has multiple constructors, it’s possible to call one constructor from the body of another one using this(). Run() is a method of Runnable interface that must be implemented by all threads. The basic condition of method overriding is that method name, arguments as well as return type must be exactly same as is that of the method being overridden. Hence using a different return type doesn’t override a method.

In the example above, we measure the execution time of a code snippet. This is a simple yet effective way to identify bottlenecks and optimize performance. We’ll delve into these questions and many more in the following sections. Once you have gained confidence after solving the basic questions, let’s increase the level of questions. Here in this section, we have listed more complex Java 8 questions.

For individuals aiming to excel in the field of software development, understanding Core Java is fundamental. Whether you’re preparing for an interview or looking to strengthen your Java programming skills, a structured Java Course https://www.trading-market.org/ can significantly enhance your proficiency. We can run a jar file using java command but it requires Main-Class entry in jar manifest file. Main-Class is the entry point of the jar and used by java command to execute the class.

It then calls the `rotateMatrixClockwise` function to rotate the matrix and prints the rotated matrix. Please note that this program assumes the user will enter valid input (the correct number of rows, columns, and matrix elements). Error handling and input validation have been omitted for brevity.

Due to ArrayLists array-based nature, it grows dynamically in size ensuring that there is always enough room for elements. When an ArrayList element is first created, the default capacity is around elements which basically depends on the Java version. ArrayList elements are copied over from the original array to the new array when the capacity of the original array is full. As the ArrayList size increases dynamically, the class creates a new array of bigger sizes and it copies all the elements from the old array to the new array. This process of dynamically growing an array is known as resizing. Since generics type information gets erased at compile time by Type Erasure, the array store check would have been passed where it should have failed.