Advanced java interview questions Java is an all-time favourite programming language in the world. According to the latest research, 90% of Fortune 500 companies use Java, and almost all Android apps are based on Java programming, with 9 million Java developers placed all around the world. And if yoRead more
Advanced java interview questions
Java is an all-time favourite programming language in the world. According to the latest research, 90% of Fortune 500 companies use Java, and almost all Android apps are based on Java programming, with 9 million Java developers placed all around the world. And if you are a developer and searching for job, then you need these questions that will help you crack advanced Java interview questions.
These questions are definitely there for your interview. And if you get these questions, then they will definitely help you with advanced Java interview questions in the future.
Q1: How does Garbage Collection prevent a Java application from going out of memory?
Answer
It doesn’t! Garbage Collection simply cleans up unused memory when an object goes out of scope and is no longer needed. However, an application could create a huge number of large objects that cause an OutOfMemoryError.
Q2: What differences exist between HashMap and Hashtable?
Answer
There are several differences between HashMap and Hashtable in Java:
- Hashtable is synchronised, whereas HashMap is not. This makes HashMap better for non-threaded applications, as unsynchronized Objects typically perform better than synchronised ones.
- Hashtable does not allow null keys or values. HashMap allows one null key and any number of null values.
- One of HashMap’s subclasses is LinkedHashMap, so in the event that you’d want predictable iteration order (which is insertion order by default), you could easily swap out the HashMap for a LinkedHashMap. This wouldn’t be as easy if you were using Hashtable.
Q3: What are function overriding and overloading in Java?
Answer
- Method overloading in Java occurs when two or more methods in the same class have the exact same name, but different parameters.
class Dog{
public void bark(){
System.out.println(“woof “);
}
//overloading method
public void bark(int num){
for(int i=0; i<num; i++)
System.out.println(“woof “);
}
}
- On the other hand, method overriding is defined as the case when a child class redefines the same method as a parent class. Overridden methods must have the same name, argument list, and return type. The overriding method may not limit the access of the method it overrides.
class Dog{
public void bark(){
System.out.println(“woof “);
}
}
class Hound extends Dog{
public void sniff(){
System.out.println(“sniff “);
}
public void bark(){
System.out.println(“bowl”);
}
}
public class OverridingTest{
public static void main(String [] args){
Dog dog = new Hound();
dog.bark();
}
}
Q4: What is reflection, and why is it useful?
Answer
The name reflection is used to describe code which is able to inspect other code in the same system (or itself) and to make modifications at runtime.
For example, say you have an object of an unknown type in Java, and you would like to call a ‘doSomething’ method on it if one exists. Java’s static typing system isn’t really designed to support this unless the object conforms to a known interface, but using reflection, your code can look at the object and find out if it has a method called ‘doSomething’ and then call it if you want to.
Method method = foo.getClass().getMethod(“doSomething”, null);
method.invoke(foo, null);
Q5: What is the difference between an exception and an error in Java?
Answer
- An Error “indicates serious problems that a reasonable application should not try to catch.”
- An Exception “indicates conditions that a reasonable application might want to catch.”
Q6: What is the difference between an Interface and an Abstract class?
Answer
Java provides and supports the creation of both abstract classes and interfaces. Both implementations share some common characteristics, but they differ in the following features:
- All methods in an interface are implicitly abstract. On the other hand, an abstract class may contain both abstract and non-abstract methods.
- A class may implement a number of interfaces but can extend only one abstract class.
- In order for a class to implement an interface, it must implement all its declared methods. However, a class may not implement all the declared methods of an abstract class. Though, in this case, the sub-class must also be declared as abstract.
- Abstract classes can implement interfaces without even providing the implementation of interface methods.
- Variables declared in a Java interface are by default final. An abstract class may contain non-final variables.
- Members of a Java interface are public by default. A member of an abstract class can either be private, protected, or public.
- An interface is absolutely abstract and cannot be instantiated. An abstract class also cannot be instantiated but can be invoked if it contains a main method.
Q7: Can == be used on enum?
Answer
Yes: enums have tight instance controls that allow you to use == to compare instances. Here’s the guarantee provided by the language specification.
Q8: How can I synchronise two Java processes?
Answer
It is not possible to do something like you want in Java. Different Java applications will use different JVM’s, fully separating themselves into different ‘blackbox’es. However, you have two options:
- Use sockets (or channels). Basically, one application will open the listening socket and start waiting until it receives some signal. The other application will connect there and send signals when it had completed something. I’d say this is a preferred method used in 99.9% of applications.
- You can call Winapi from Java (on Windows).
Q9: Is Java pass-by-reference or pass-by-value?
Answer
Java is always pass-by-value. Unfortunately, when we pass the value of an object, we are passing the reference to it. There is no such thing as “pass-by-reference” in Java. This is confusing to beginners.
The key to understanding this is that something like
Dog myDog;
is not a dog; it’s actually a pointer to a dog.
So when you have
Dog myDog = new Dog(“Rover”);
foo(myDog);
you’re essentially passing the address of the created Dog object to the foo method.
Q10: Is there anything like static class in Java?
Answer
Java has no way of making a top-level class static but you can simulate a static class like this:
- Declare your class final. – Prevents extension of the class since extending a static class makes no sense
- Make the constructor private. – Prevents instantiation by client code, as it makes no sense to instantiate a static class
- Make all the members and functions of the class static – Since the class cannot be instantiated, no instance methods can be called or instance fields can be accessed
- Note that the compiler will not prevent you from declaring an instance (non-static) member. The issue will only show up if you attempt to call the instance member
How person get help with these advanced java interview questions
Advanced Java interview questions can help a person in many different ways.
Preparing for technical interviews: Advanced Java interview questions are frequently asked technically for senior or specialised roles. Familiarity with these questions boosts applicants’ confidence during the interview process.
Demonstrating in-depth knowledge: Advanced Java questions measure a candidate’s grasp of advanced Java programming principles and capabilities. Answering these questions effectively displays a strong mastery of Java, which improves the candidate’s profile and helps you crack advanced java interview questions
Highlighting problem-solving abilities: Many advanced Java problems include challenging problem-solving scenarios. Answering these questions displays not just technical knowledge but also a candidate’s ability to approach and solve complex challenges.
Operations on strings in Java Introduction to Operations on strings in java Welcome to the world of Java, where string operations are made simple, and if you want to know about operations on strings in Java, then you are at right blog In this blog, we will be discussing the String class in Java andRead more
Operations on strings in Java
Introduction to Operations on strings in java
Welcome to the world of Java, where string operations are made simple, and if you want to know about operations on strings in Java, then you are at right blog In this blog, we will be discussing the String class in Java and its various features, such as string creation, concatenation of strings, substring extraction, comparing strings in terms of content and reference, searching for characters/ or substrings inside a string, manipulating strings and case conversion, as well as extracting characters from a string. Let’s get into the details.
Class of operations on strings in Java
Strings are an essential part of any programming language, and the class of operations on strings in Java is no different. Strings provide an array like sequence of characters that can be used to store text based data. The String class provides numerous methods that can be used to manipulate strings, including substring extraction, character extraction, and much more. Additionally, it also provides methods for comparing two strings against each other, either by content or reference.
Creation of Strings
Creating a new string is straightforward in Java. You can use the new keyword to create a new instance of the String class or you can use the string literal syntax which allows you to directly specify your desired value inside double quotes (” “). Both of these approaches will result in a new string object being created.
Concatenation & Substring Extraction
Once you have created a new string object you can easily concatenate it with other strings using one of the several provided methods such as .concat() or + operator. Additionally, you can also extract portions from an existing string using the .substring() method which allows you to specify start & end indices while creating a substring from your existing string.
What is String in Java?
Understanding the concept of a string and what it means in Java is an essential part of coding. And what it actually mean to do operations on strings in Java? A string, simply put, is a sequence of characters. In Java, strings are handled by the String class, which contains various methods for performing operations on a string.
When dealing with operations on strings in Java, there are several operations that you can perform on them. Common operations include concatenating strings together, finding the length of a string, comparing two strings to see if they are equal or not, searching within a string for certain characters, and replacing parts of a string with others.
Java’s String class has many useful methods that make it easier to work with strings. One such method is the substring method, which allows you to create a new string using parts of an existing one. Another helpful method is the trim() method, which removes any leading or trailing whitespace from your strings.
There are also object wrappers available for integers, floats, and other primitives that allow you to use the same kinds of methods when dealing with those data types, like you would with strings. For example, you can use the Integer class to convert an integer into a string and vice versa using their respective parseXxx() and valueOf() methods.
Overall, understanding what strings are and how to manipulate them in Java is important for anyone looking to create efficient code or someone who wants to do operations on strings in Java. With basic knowledge of the different operations you can perform on strings as well as being familiar with the many helpful methods provided by Java’s String class, you’ll be able to easily work with them in no time!
Finding a Character for operations on strings in Java
Finding a character in a string is an important concept to understand when working with operations on strings in Java. Whether you are coding for a project, building your own application, or just sharpening your programming skills, this guide will provide an introduction to finding characters in a string and the operations that help you do so.
When it comes to finding characters in a string, there are several methods and operations that can help you do so. Let’s take a look at some of the most useful operations for finding characters in a string: the indexOf() method, the substring() method, and the charAt() method.
The indexOf() method is used to determine the first occurrence of a character or substring within another string. This operation returns the index position of the given character or substring if it exists, or 1 if it does not exist within the given string. For example, if we wanted to find out whether an ‘@’ symbol existed within a given email address, we could use indexOf(‘@’) to check if it existed.
The substring() method is used to return part of another string or even an entire string up until certain characters are found. Substring() takes two parameters: a starting index (included) and an ending index (not included). This operation can be useful when trying to conditionally extract only certain portions of a given string such as retrieving usernames from email address strings.
Finally, the charAt() method is used to retrieve individual characters within a given string at specified indices. Similar to substring(), charAt() takes one parameter: an integer representing the position within the given string which is 0based indexed.
How to create a string object?
Creating a string object in Java is a necessary part of any program to understand when working with operations on strings in Java. Strings are one of the most important data types used in programming. Whether you’re building an application or carrying out an operation such as manipulating or querying string data, understanding how to create a string object is essential.
There are two primary methods for creating a string object: using string literals and using the ‘new’ keyword.
String literals are the simplest way to create strings. This involves writing the text between two quotation marks “like this” and assigning it to a variable. For example, you could declare a string literal in Java by writing:
String userName = “John”;
The other method is through the ‘new’ keyword which creates objects from classes. To do this, you need to write ‘new String ()’ followed by the text (e.g., new String (“John”)). The object is then assigned to a variable like this:
String userName = new String(“John”);
Using both these methods, once the object has been created you can carry out operations on it such as finding its length or replacing certain characters. For example, if you wanted to find the length of userName written above you could use .length() like so:
int nameLength = userName.length();
This would assign 4 (the number of characters in “John”) to nameLength. Alternatively, if you needed to replace all instances of one character within your string with another character, you could use .replace() like this:
userName.replace
Finding the Length of a String
After understand the operations on strings in Java start Working with text strings is a fundamental part of programming, and finding the length of a string is a common operation that must be performed. In Java, there are several methods you can use to find the length of a string.
The simplest approach is to make use of the builtin length() method. This method returns an integer value specifying how many characters are present in the string. To access this method, all you need to do is call it on the string object, like this: StringName.length().
Another option for finding the length of a string involves using it for each loop iteration. By using this approach, you iterate over each character within a given string and count them as you go. This approach may be slightly more complicated, but it comes with the added benefit of allowing additional operations on each character as they are encountered during iteration.
Furthermore, if you would like to manipulate strings in more advanced ways, consider making use of the StringBuilder class. This class offers more sophisticated methods for manipulating strings, such as insert(), replace(), and delete(). However, these come with their own set of complexities that should be taken into account before attempting complex operations on strings in Java.
For further information on how to perform operations on strings in Java, refer to the official Java API documents, which contain detailed explanations and examples for all related topics. With this information at your fingertips, you’ll have all you need to work confidently with strings in Java, learn to find their lengths quickly and easily and also learn all thing related to operations on strings in Java
Comparing Strings
If you’re programming in Java and need to compare strings, you have plenty of tools available. String operations are an important part of any Java program, and there are a variety of methods and techniques you can use to compare strings. This article covers the basics of string comparison in Java, including string methods,.equals(),.compareTo(), character at index, substring extraction, ASCII value comparison, collation sequence comparison, and performance aspects.
String methods are basic functions that allow you to interact with strings in various ways. You can use a string method to search and replace characters or to extract a substring from within a larger piece of text. One popular string manipulation method is.equals(), which allows you to compare two strings for equality by returning either true or false.
Alternatively, you can use the similar .compareTo() function to compare strings for greater than/less than value. This method returns an integer indicating the amount by which the two strings differ from each other by numerical value (positive for greater than and negative for less than). You can also access individual characters within strings by using ‘character at index’, which will retrieve characters from specific indexes within a larger piece of text.
Substring extraction is another helpful tool when comparing strings. This process allows you to pull out sections of larger textual content so they may be compared against other substrings or against entire pieces of text independently. The ASCII values of individual characters within any given string can also be accessed if necessary; these values can then be compared against one another for exact matches or partial matches as desired.
Replacing Characters in a String
Replacing Characters in a String is an important task that’s often necessary to successfully process data and is one of important operations on strings in Java. If you’re working with the Java language, you’ll need to understand the various methods and parameters used to replace characters in a string.
In order to better understand how character replacement works, it’s important to first review the basics of string data types and operations. The String class is one of the most common classes used in Java, and any data structure deemed a string’ consists of characters within quotation marks (e.g., “ABC123”). From here, operations can be performed on strings, such as the insertion, deletion, and replacement of individual characters.
When replacing characters in a string with Java, there are two main methods you may use: replace() or replaceAll(). Both accept at least two parameters – a regular expression and an argument (which could be either a string or an object). It can also take up to four arguments if you wish to take advantage of additional features, such as matching character sequences within the string that match certain criteria.
Let’s look at how this applies when replacing characters in a string by using basic syntax. Firstly, let’s use the replaceAll() method: str1.replaceAll(“w”, “x”); This statement would replace all alphanumeric characters with an ‘x’ within str1. On the other hand, if we wanted to use replace(), we’d have to write something like this: str1.replace(“a”, “z”); This would replace all occurrences of ‘a’ with ‘z’ within str1.
Why does Java use the concept of a string literal?
The concept of string literals has been around for a long time, but it wasn’t until Java introduced the concept that it had any real use. String literals are used in Java to interpret and represent a sequence of characters as a single entity. This is especially valuable when performing operations on strings in Java, as it allows developers to manipulate one single string object instead of treating several separate characters as individual items.
For example, if you wanted to change the case of all the characters in a string from uppercase to lowercase or vice versa, you could easily do so by using a single operation on your string literal instead of writing code that would have to treat each character individually. Additionally, using string literals makes your programs more flexible and easier to read and maintain.
Another benefit of using string literals is that they are immutable; this means that once the code has evaluated them, the contents of the literal cannot be changed without creating another instance altogether. Immutability makes strings more secure and much easier to work with, especially when dealing with multithreaded applications where multiple threads can access and modify an object concurrently.
Ultimately, using string literals makes operations on strings in Java simpler and faster, while also providing protection against unintended changes due to their immutability. So if you’re looking for an easy way to manipulate strings in your programs, string literals are a great option!
Java String class methods
The Java String class is a powerful tool for manipulating strings in a Java program. It provides several methods that can help you perform many different operations on strings in Java. By understanding the fundamental methods of the String class, you can easily write code to manipulate strings in your own programs.
One useful way to use the String class is by using its methods to perform basic operations on strings in Java. You can do things like create new string variables based on existing string variables, concatenate strings together (add them together), compare two strings, and search for specific characters or substrings in a string.
For example, let’s say you have a string containing the phrase “Hello world”. To capitalize the first letter in the string, you could use the replaceFirst() method, which takes two arguments: a regular expression as its first argument that specifies what will be replaced, and a replacement string as its second argument that replaces it with whatever you specify. In this case, we could use replaceFirst(“^[az]”,”H”) to capitalize the first character of our “Hello world” string.
You can also use Java String methods to search for specific characters or substrings within a string. The indexOf() method allows you to specify what character or substring you want to search for and returns an integer representing the position at which it appears within the original string (or 1 if it isn’t found). This makes it convenient to find occurrences of certain words or phrases in your data.
Finally, if you need to compare two strings and determine their equality status, there are two helpful methods available: equals() and compareTo().
Conclusion
When it comes to operations on strings in Java, you should now have a good understanding of the various methods and functions available to you. From concatenating strings to extracting substrings, there are plenty of options to help you manipulate a string in a variety of ways. Taking advantage of these string operations will enable you to create complex and customized solutions for your programming tasks.
If you’re just starting out with Java, then you need understand operations on strings in Java and working out the details of how operations on strings in Java work can be challenging. However, by taking the time to understand these methods and functions, you can become much more comfortable manipulating strings in your code. This will help make development more efficient and save time while creating robust solutions.
Finally, it’s important to remember that the best way to become an expert with string operations is by experimenting with code examples and practical applications. With enough practice, manipulating strings using Java will become second nature. So dive today into the world of operations on strings in Java and unlock the power of powerful coding solutions!
Frequently Asked Questions
How do I perform different operations on strings in Java?
What is the + operator in Java?
What is a string object in Java?
What are the functions of string class in Java?
We hope you understand operations on strings in Java with our article, and this will help you with future projects related to operations on strings in Java.