, Driver Exam
, Read First Line
, Max Sum
, Paper Strip
, Unloading Trucks
, Read Write Execute
, Shining Star
, ATM Locations
, Ban Users
, Bank Branches
, Chain Link
, Cheapest Product
, Crop Ratio
, Date Transform
, Document Counter
, Employee Manager
, Hospital Patients
, Index Performance
, Menu Items
, Merge Stock Index
, Movies Live
, Restaurant Menu
, SMS Messages
, Student Activities
, Youngest Child
, Internal Nodes
, Log Parser
, Remove Repetitions
, Snow Storm
, Stack to List
, Test Results
, Unique Product
, Unique Numbers
, Weighted Average
, Language Teacher
, Manager Sales
, Delete Orders
, Book Sale
, Average Salary
, Movie Genres
, Auto Show
, Shelf Test
, Moving Total
, Kilometer Converter
, Department Report
, Student Rankings
, Welfare Organization
, Student Max Score
The Java programming language is a simple, modern, general-purpose, object-oriented programming language. Having a basic familiarity with the programming language used on the job is a prerequisite for quickly getting up to speed.
Everyone makes mistakes. A good programmer should be able to find and fix a bug in their or someone else's code.
A programmer should use a language as a tool, always taking advantage of language-specific data types and built-in functions.
A stream is a sequence of data elements made available over time. It is particularly useful for tasks that may benefit from being asynchronous, including tasks such as I/O processing or reading from a file, and as such is important for developers to understand.
The string data structure is used to represent text. It is one of the most commonly used data structures. Therefore, every programmer should be skilled at string manipulation.
Exceptions exist in most modern programming languages, making it important for a programmer to understand them and know how to handle them.
Arithmetic is a fundamental branch of mathematics. An understanding of arithmetic concepts, and their application, is important for every candidate.
SQL is the dominant technology for accessing application data. It is increasingly becoming a performance bottleneck when it comes to scalability. Given its dominance, SQL is a crucial skill for all engineers.
Conditional statements are a feature of most programming and query languages. They allow the programmer to control what computations are carried out based on a Boolean condition.
A database view is a result set that is defined by a stored query, the results of which can can also be queried. As a fundamental and widely used database construct, it's useful for candidates to understand how and when they should be used.
When designing and/or analyzing an algorithm or data structure, it is important to consider the performance and structure of an implementation. Algorithmic thinking is one of the key traits of a good programmer, especially one working on complex or performance-critical code.
An array is a container of a fixed number of objects of a similar type. It is a fundamental component of most programming languages.
Subqueries are commonly used in database interactions, making it important for a programmer to be skilled at writing them.
The UPDATE statement is used to modify the existing records in a table and is one of the most used operations for working with the database.
Every programmer should be familiar with data-sorting methods, as sorting is very common in data-analysis processes.
Test-driven development (TDD) is a software development process that relies on the repetition of a very short development cycle: requirements are turned into very specific test cases, based on which the software is improved only in order to pass the new tests. TDD is an essential skill for modern programmers.
Memory management allows programs to request memory dynamically from the operating system, and free it for reuse when no longer needed. Many modern programming languages automate this process; however, it should still be an important consideration when implementing an application.
Constraints are used to define rules and relationships. They are applied to a dataset. A constraint may take many forms, such as x ≤ 5 in a programming language and a NOT NULL constraint in a SQL table definition.
The CREATE TABLE statement is used to create a new table in a database. It is an essential command when creating new database.
A database schema defines how data is stored in a database. An SQL database uses a schema to define tables consisting of rows and columns that use fixed data types to store data. Formalizing how data is stored is the first step towards building an application or service.
The SELECT statement is used to select data from a database. It is the most used SQL command.
The CREATE INDEX statement is used to create indexes for tables. Indexes are used to retrieve data from the database more quickly. They are very important for making performant queries.
The performance of an application or system is important. The responsiveness and scalability of an application are all related to how performant an application is. Each algorithm and query can have a large positive or negative effect on the whole system.
The ALTER TABLE statement is used to add, delete, or modify columns and constraints in an existing table. Alter table statements are important for all programmers who have to modify existing schemas.
A linked list is a linear collection of data elements where each element points to the next. It is a data structure consisting of a collection of nodes which together represent a sequence. It is usually used for advanced scenarios where we need fast access to the next element, or when we need to remove an element from anywhere in the collection.
An aggregate function is typically used in database queries to group together multiple rows to form a single value of meaningful data. A good programmer should be skilled at using data aggregation functions when interacting with databases.
Knowing how to order data is a common task for every programmer.
Integer division is division in which the fractional part (remainder) is discarded. Knowing this is important for optimal implementation of some algorithms and for avoiding common bugs.
A regular expression (regex) is a special text string for describing a search pattern. It is a common way for extracting data from text.
Object-oriented programming is a paradigm based on encapsulating logic and data into objects, which may then contain fields and procedures. Many of the most widely used programming languages are based on OOP, making it a very important concept in modern programming.
The process of restructuring existing computer code without changing its external behavior. It is essential for keeping code readable and maintainable.
LEFT JOIN is one of the ways to merge rows from two tables. We use it when we also want to show rows that exist in one table, but don't exist in the other table.
A queue is a collection of items that are maintained in a sequence and can be modified by the addition of entities at one end of the sequence and removal from the other end of the sequence. It is the collection to be used when first-in-first-out (FIFO) collection is needed.
A HashMap (or dictionary) is a data type composed of a collection of key-value pairs, where each possible key appears at most once in the collection. It is used when we need to access items by their keys.
Iteration is the act of repeating a process, or cycling through a collection. Iteration is one of the fundamental flow control tools available to developers.
Lists are collections that act as dynamic arrays. Lists offer the flexibility of dynamically sized arrays, the simplicity of access of arrays, and are more performant than more ubiquitous collections in most scenarios.
The proper implementation and use of indexes are important for improving the performance of database queries.
The UNION operator is used to combine the result-set of two or more SELECT statements. It is often used when a report needs to be made based on multiple tables.
The GROUP BY statement groups rows by some attribute into summary rows. It is a common command when making various reports.
Even though most database insert queries are simple, a good programmer should know how to handle more complicated situations like batch inserts.
A normalized database is normally made up of multiple tables. Joins are, therefore, required to query across multiple tables.
A tree is a hierarchical structure defined recursively starting with the root node, where each node is a data structure consisting of a value, together with a list of references to other nodes (the "children"). A lot of problems can be solved efficiently with trees, which makes them important for developers.
Familiarity with data serialization to and from formats such as XML and JSON is important as it is commonly used for interprocess communication
Extensible Markup Language (XML) is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. The design goals of XML emphasize simplicity, generality, and usability across the Internet. This is one of the most used formats for exchanging data over the web.
A good programmer should be familiar with when to use recursive functions, since they can provide elegant solutions for complex problems.
Choosing the right data structure to solve a problem can have huge implications on the performance of an application. Knowing when to use a specific data structure is one of the most important skills for a programmer.
Access modifiers like public, protected, or private should be used to specify accessibility levels - who can access the object or some of its parts. They are one of the key points for writing maintainable object-oriented code.
Multi-threading allows a process to make more efficient use of modern hardware by allowing code to execute asynchronously. It can drastically improve the performance of any app; however, it can be tricky to get right, making this an important topic for any programmer.
When using multithreading, developers need to know how to make one thread wait for another to finish its task before continuing with its work.
Since a string is an immutable data structure, concatenating multiple strings can introduce significant performance penalties. Every experienced developer should know when to use StringBuilder instead of simply concatenating two strings to improve performances in such scenarios.
The ArrayList class acts like a resizable array. It is used when there is a need for an array that can have a variable size.
A good programmer should be able to analyze and plan for the performance of an algorithm.
A stack is dynamic data container that follows the Last In First Out (LIFO) principle. Developers should use stack when the last item to be inserted into a container is the first one to be deleted from it.
Stream API is used to process collections of objects. It supports various methods, such as mapping, filtering, and sorting, which can be pipelined to produce the desired result. Since it simplifies code and improves productivity, it should be well known to Java programmers.
Class modifiers like abstract, final, or static should be used to specify how a class should be used and what is allowed or not allowed to be done with it. This is an essential topic for OOP programming.
In object-oriented programming, inheritance is the mechanism of basing a class upon another class, retaining similar implementation. Inheritance allows programmers to reuse code and is a must know topic for every programmer who works with OOP languages.
A CTE (Common Table Expression) is a temporary result set that can be referenced within another SELECT, INSERT, UPDATE, or DELETE statement. Recursive CTEs can reference themselves, which enables developers to work with hierarchical data.
The delete statement is used to delete records in a table and is one of the four basic CRUD functions (create, read, update, and delete) required for working with any persistent storage.
Many real-life situations are best modeled by graphs. Therefore, an in-depth knowledge of graph data structures is important for a good programmer.
Test case design
The CASE statement is SQL's control statement. It goes through conditions and returns a value.
Test case design
Being able to create a set of test cases that ensure adequate test coverage is a key skill for creating a successful test. It is desirable for the test suite also to be optimal, i.e. to minimize test execution effort and time without affecting the test coverage.
Unit testing is a type of software testing where individual units or components of a software are tested. Unit testing of software applications is done during the development (coding) of an application and should be well known practice to any developer.
HashSet is container that stores unique elements in no particular order. This allows for fast checks to see if a value was already added.
Method overriding, in object-oriented programming, is a language feature that allows a subclass to provide a specific implementation of a method that is already provided by one of its parent classes.
Higher order function
Dynamic programming methods for code optimization can be very useful to a programmer who understands them.
Higher order function
A higher order function is a function that takes another function as an argument, or returns another function. Developers often use them for writing reusable code.
An interface is used to define an abstract type that defines behaviors as method signatures. Instances of different types can implement the same interface and provide a way for a developer to reuse the code.