Java Interview Question

Categories: Java 8(JDK1.8)

What is the purpose of using javap?

The javap command disassembles a class file. The javap command displays information about the fields, constructors and methods present in a class file.

Syntax

javap fully_class_name


Can you access the private method from outside the class?

Yes, by changing the runtime behavior of a class if the class is not secured.


What are wrapper classes?

Wrapper classes are classes that allow primitive types to be accessed as objects. In other words, we can say that wrapper classes are built-in java classes which allow the conversion of objects to primitives and primitives to objects. The process of converting primitives to objects is called autoboxing, and the process of converting objects to primitives is called unboxing. There are eight wrapper classes present in java.lang package is given below.


What are autoboxing and unboxing? When does it occur?

The autoboxing is the process of converting primitive data type to the corresponding wrapper class object, eg., int to Integer. The unboxing is the process of converting wrapper class object to primitive data type. For eg., integer to int. Unboxing and autoboxing occur automatically in Java. However, we can externally convert one into another by using the methods like valueOf() or xxxValue().


It can occur whenever a wrapper class object is expected, and primitive data type is provided or vice versa.

a) Adding primitive types into Collection like ArrayList in Java.

b) Creating an instance of parameterized classes ,e.g., ThreadLocal which expect Type.

c) Java automatically converts primitive to object whenever one is required and another is provided in the method calling.

d) When a primitive type is assigned to an object type.


What is object cloning?

The object cloning is a way to create an exact copy of an object. The clone() method of the Object class is used to clone an object. The java.lang.Cloneable interface must be implemented by the class whose object clone we want to create. If we don't implement Cloneable interface, clone() method generates CloneNotSupportedException. The clone() method is defined in the Object class. The syntax of the clone() method is as follows:


protected Object clone() throws CloneNotSupportedException


What are the advantages and disadvantages of object cloning?

Advantage of Object Cloning

a) You don't need to write lengthy and repetitive codes. Just use an abstract class with a 4- or 5-line long clone() method.

b) It is the easiest and most efficient way of copying objects, especially if we are applying it to an already developed or an old project. Just define a parent class, implement Cloneable in it, provide the definition of the clone() method and the task will be done.

c) Clone() is the fastest way to copy the array.

Disadvantage of Object Cloning

a) To use the Object.clone() method, we have to change many syntaxes to our code, like implementing a Cloneable interface, defining the clone() method and handling CloneNotSupportedException, and finally, calling Object.clone(), etc.

b) We have to implement the Cloneable interface while it does not have any methods in it. We have to use it to tell the JVM that we can perform a clone() on our object.

c) Object.clone() is protected, so we have to provide our own clone() and indirectly call Object.clone() from it.


What is a native method?

A native method is a method that is implemented in a language other than Java. Natives methods are sometimes also referred to as foreign methods.


What is the purpose of the strictfp keyword?

Java strictfp keyword ensures that you will get the same result on every platform if you perform operations in the floating-point variable. The precision may differ from platform to platform that is why java programming language has provided the strictfp keyword so that you get the same result on every platform. So, now you have better control over the floating-point arithmetic.


What is the purpose of the System class?

The purpose of the System class is to provide access to system resources such as standard input and output. It cannot be instantiated. Facilities provided by System class are given below.

a) Standard input

b) Error output streams

c) Standard output

d) utility method to copy the portion of an array

e) utilities to load files and libraries


 Which containers use a border layout as their default layout?

The Window, Frame and Dialog classes use a border layout as their default layout.

Top Blogs
Java Retention Policy, SOURCE,CLASS,RUNTIME Published at:- Meaning Of Java Published at:- Java Programming in Python Published at:- Applications of Java Programming Published at:- Java Explaination Published at:- History of Java Published at:- Tools You Will Need Published at:- Local Environment Setup Published at:- Popular Java Editors Published at:- Basic Syntax in Java Published at:- Java Identifiers Published at:- Java Modifiers Published at:- Inheritance Published at:- Object and Classes In Java Published at:- Classes in Java Published at:- Source File Declaration Rules Published at:- Java Package Published at:- Constructors Published at:- No argument Constructors Published at:- Basic Datatypes In Java Published at:- Java - Modifier Types Published at:- Java - Basic Operators Published at:- The Relational Operators Published at:- The Bitwise Operators Published at:- The Logical Operators Published at:- The Assignment Operators Published at:- Miscellaneous Operators Published at:- Precedence of Java Operators Published at:- Java - Loop Control Published at:- Java - Decision Making Published at:- Java - Numbers Class Published at:- Java In Character Class Published at:- Escape Sequences In Java Published at:- Character Methods In Java Published at:- Java In Strings Class Published at:- String Length In Java Published at:- Concatenating Strings In Java Published at:- Creating Format Strings In Java Published at:- Java - Arrays Published at:- Creating Arrays In Java Published at:- Java - Date and Time Published at:- Getting Current Date and Time Published at:- Date Comparison Published at:- Simple DateFormat Format Codes Published at:- Sleeping for a While Published at:- Gregorian Calendar Class Published at:- Java - Regular Expressions Published at:- Java - Methods Published at:- Method Calling Published at:- Passing Parameters by Value In Java Published at:- Method Overloading In Java Published at:- The finalize( ) Method In Java Published at:- Java - Files and I O Published at:- Standard Streams In Java Published at:- File Input Stream Published at:- File Output Stream In Java Published at:- Directories in Java Published at:- Java - Exceptions Published at:- Exception Hierarchy In Java Published at:- Java Programming Language Published at:- JDK in Java Published at:- History of Java Programming Language Published at:- Difference Between C++ vs Java vs Python Published at:- How JVM Works – JVM Architecture? Published at:- JVM Memory Published at:- Difference between Byte Code and Machine Code Published at:- How is Java platform independent? Published at:- Java is platform-independent but JVM is platform dependent Published at:- Java Basic Syntax Published at:- Data types in Java Published at:- Primitive data type vs. Object data type in Java with Examples Published at:- Java Identifiers Published at:- Operators in Java Published at:- Variables in Java Published at:- Types of Variables in Java Published at:- Differences between the Instance variable Vs. the Static variables Published at:- Scope of Variables In Java Published at:- Differences between JDK, JRE and JVM Published at:- Similarities and Difference between Java and C++ Published at:- Setting up the environment in Java Published at:- Packages In Java Published at:- Decision Making in Java (if, if-else, switch, break, continue, jump) Published at:- Loops in Java Published at:- Java while loop with Examples Published at:- Java do-while loop with Examples Published at:- Components of do-while Loop Published at:- Continue Statement in Java Published at:- Break statement in Java Published at:- Define Java Methods Published at:- Java Method Parameters Published at:- Return Values In JAva Published at:- Define of Java Scope Published at:- Meaning of Java Recursion Published at:- What is OOP in Java ? Published at:- Java Class Attributes Published at:- Java Class Methods Published at:- Static vs. Non-Static Java Published at:- Java Constructors Published at:- Java Encapsulation Published at:- Java Packages Published at:- Java Inheritance Published at:- Java Polymorphism Published at:- Java - Abstraction Published at:- Java - Interfaces Published at:- Declaring Interfaces In Java Published at:- Java - Overriding Published at:- Java - Packages Published at:- Java - Data Structures Published at:- Java - Data Structures Published at:- The Collection Interfaces In Java Published at:- Generics In Java Published at:- Java - Serialization Published at:- Java - Networking Published at:- Java - Sending Email Published at:- Java - Multithreading Published at:- Java - Applet Basics Published at:- Java - Documentation Comments Published at:- Comments in Java Published at:- Java Interview Questions Set 1 Published at:- Java Interview Questions Set 2 Published at:- Java Interview Questions Set 2 Published at:- Java Interview Questions Set 3 Published at:- Java Interview Questions Set 4 Published at:- Java Interview Questions Set 5 Published at:- Java Interview Questions Set 6 Published at:- Java Interview Questions Set 7 Published at:- Java Interview Questions Set 8 Published at:- Java Interview Questions Set 9 Published at:- Java Interview Question Set 10 Published at:- Java Interview Question Set 11 Published at:- Java interview Question Set 12 Published at:- Java Interview Question Set 13 Published at:- Java Interview Questions Set 10 Published at:- Java Interview Question Set 12 Published at:- Java Interview Question Set 13 Published at:- Java Interview Question Set 14 Published at:- Java Interview Question Set 15 Published at:- Java Multithreading Interview Questions Set 1 Published at:- Java multithreading interview questions Set 2 Published at:- Java multithreading interview questions Set 3 Published at:- Java Multithreading Interview Set 4 Published at:- Java multithreading interview questions Set 5 Published at:- Java collections interview questions Set 6 Published at:- Java collections interview questions Set 7 Published at:- Java Interview Question Set 8 Published at:- Java Interview Question Set 1 Published at:- Java Interview Question Set 10 Published at:- Java Interview Question Published at:- Java Interview Question Published at:- Java Interview Question Published at:- Java Interview Question Published at:- Java Interview Question Published at:- Java Interview Question Published at:- Java Interview Question Published at:- JavaScript Interview Questions Published at:- Javascript Interview Question Published at:- Javascript Interview Question Published at:- JavaScript Interview Question Set 1 Published at:- JavaScript Interview Question Set 2 Published at:- JavaScript Interview Question Set 3 Published at:- JavaScript Interview Question Set 4 Published at:- Python Interview Question Set 6 Published at:- How to Optimize Java Apps on Kubernetes Published at:- When and Why Java is utilized for Application Improvement Published at:- Scanner nextLine() ,nextInt() ,nextDouble() method in Java with Examples Published at:- java toUpperCase() and toLowerCase() example Published at:- pushing value at last in java | how to add element at the end of array in java Published at:- Write a program for group words by first character of given string | Java 8 Stream Example Published at:- Write a Java 8 program to calculate the age of a person in years given their birthday Published at:- Write a Java 8 program to calculate the age of a person in years given their birthday Years Months Days Published at:- Write a Java 8 program to print the first 10 odd numbers Published at:- Filter employees by age in Java 8 Lamda steam Published at:- Write a Java 8 program to get the last element of an array string/object Published at:- Filter employees by age set senior if age is greater than 30 in Java 8 Lamda steam Published at:- How to increment salary by 2%, 5%, etc. Using java Published at:- Write a program to find the only duplicate count list in the List Published at:- Write a program to append char in char ex-input- {A, B, C} output->[A_X, B_Y, C_Z] Published at:- Write a program to sum an array without using the sum method Published at:- Write a program to sum an array Published at:- Drop all while condition not meet dropWhile(),dropWhile(Predicate<T> predicate) Published at:- Find the maximum value in a list of integers using Stream & Method Reference Published at:- How to sort a list of strings by length using Lambda expressions Published at:- How to filter and collect a list of strings that start with a specific letter using Java 8 Stream Published at:- Write a Java program To create a map from a array of strings where the key is the string and the value is its length Published at:- How to count the number of occurrences of a given word in a list of strings using Java 8 Published at:- How to remove all duplicates from an array of integers in Java using Java 8 Published at:- How to find next, previous, tomorrow ,yesterday date using Java 8 Published at:- How to iterate and modify values in a Map using Java 8 Published at:- How to print keys & values of a Map using Java 8 Published at:- count of each character in a String using Java 8 Published at:- Write a Program to find the Maximum element in an array Published at:- How to check if list is empty in Java 8 using Optional Published at:- Find duplicate elements with its count using Java 8 Published at:- Find Last duplicate character of given string using Java 8 Published at:- Given a list of integers, separate odd and even numbers Published at:- java 8 using lambda expression and stream api | Java 8 Programs using Lambda Expression and Stream Published at:- 26 Java 8 Programs using Lambda Expression and Stream Published at:- Java 8 Stream String Null Or Empty Filter Published at:- sum ,min ,max etc example using reduce method using Java 8 Stream API Published at:- Find first repeated character in a string Published at:- Sort highest salary in each department Published at:- Grouping Employees by City and Age Published at:- Finding the Count of Male and Female Employees Published at:- Printing Names of All Departments from Employee Class using Java Published at:- Printing Employee Details by Age Criteria using Java Published at:- Finding Maximum Age of Employee using Java Published at:- Printing Average Age of Male and Female Employees using Java Published at:- Printing the Number of Employees in Each Department using Java Published at:- Java Class subclass interview coding questions Published at:- Child and Parent overridden methods Throws RuntimeException Published at:- Child and Parent overridden methods Throws checked exception Published at:- Find Customer staring with +91 mobile number Published at:- Sorting the Employees Salary in Each Department in Descending Order Published at:- Sorting the Employees Salary in Each Department in Ascending Order Published at:-
R4R.co.in Team
The content on R4R is created by expert teams.