Oracle Interview Questions and Answers for Freshers

Q1. Basic account , related to project
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Q2. Behavioural questions
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Q1. Given an array of strings, print all the possible combinations of strings created by picking one character from each string of the array. The individual strings do not contain any duplicates. Ex: {ABC, DE...read more
Ans. 
Print all possible combinations of strings by picking one character from each string in the array.
• Iterate through each character of the first string and combine it with each character of the second string.

• Repeat the process for all strings in the array to get all possible combinations.

• Use nested loops to generate combinations efficiently.
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Q2. Given an array of size n, print the indices , i which have an equilibrium point around them defined as sum of i-p to i-1 elements = sum of i to t+p-1 elements (equal sum on left side and right side of the ...read more
Ans. 
Find indices in an array where the sum of elements around them is equal.
• Equilibrium point is defined as sum of elements before index i equals sum of elements from index i to t+p-1.

• Example: For P=2 and Array={1,-1,3,-3,10,-10,17}, indices 2, 4, and 5 are equilibrium points.

• At index 2: Left sum (1 + -1) = 0, Right sum (3) = 3; not an equilibrium.

• At index 4: Left sum (1 + -1 + 3 + -3) = 0, Right sum (10 + -10) = 0; equili...read more
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Q1. Check if given string has Balanced Parentheses.
Ans. 
Check if a string has balanced parentheses.
• Use a stack to keep track of opening parentheses.

• Iterate through the string and push opening parentheses onto the stack.

• When a closing parenthesis is encountered, pop from the stack and check if it matches the closing parenthesis.

• If stack is empty at the end and all parentheses are matched, the string has balanced parentheses.
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Q2. Modified Balanced Parentheses where a character can be matched with any other character, i.e. / with &, ! with ? and so on.
Ans. 
Modified Balanced Parentheses where characters can be matched with any other character.
• Use a stack to keep track of opening characters

• When encountering a closing character, check if it matches the top of the stack

• If it matches, pop from the stack, else return false

• Continue until end of string, return true if stack is empty
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Q3. Very similar to print the spiral order traversal of a matrix
Ans. 
Traverse a matrix in spiral order, collecting elements layer by layer.
• Start from the top-left corner and move right until the end of the row.

• Then, move down the last column.

• Next, move left across the bottom row.

• Finally, move up the first column.

• Repeat the process for the inner layers until all elements are traversed.

• Example: For a matrix [[1,2,3],[4,5,6],[7,8,9]], the spiral order is [1,2,3,6,9,8,7,4,5].
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Q1. Given a date in string format, write a java program to return the date n days after the given date. Solve the question without using DateTimeFormatter or any similar Date parsing libraries.
Ans. 
Java program to calculate date n days after given date without using Date parsing libraries.
• Parse the input date string to extract day, month, and year components.

• Calculate the total number of days represented by the input date.

• Add the specified number of days to the total days calculated.

• Convert the final total days back to day, month, and year components to get the new date.
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Q1. Java OOP questions: Function overloading and overriding, use of static function, difference between final, finally and finalize keywords.
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Q2. Print all Pythagorean triplets within a given range.
Ans. 
Print Pythagorean triplets within a given range.
• Iterate through all possible combinations of a, b, and c within the given range

• Check if a^2 + b^2 = c^2 for each combination

• Print the triplets that satisfy the Pythagorean theorem
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Q3. Print all combinations of numbers in an array which sum up to a number k. Ex : Arr={3,1,4,5} k=5 Ans : {{1,4},{5}}
Ans. 
Use backtracking to find all combinations of numbers in an array that sum up to a given number.
• Start by sorting the array in non-decreasing order to easily identify combinations.

• Use backtracking to recursively find all combinations that sum up to the target number.

• Keep track of the current combination and the remaining sum as you traverse the array.

• Add the current combination to the result when the sum equals the targe...read more
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Q4. Standard behavioural questions: Why Oracle? Where do you see yourself in 5 years? Your strengths and weaknesses.
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Q1. Two sum problem in c sharp
Ans. 
The Two Sum problem involves finding two numbers in an array that add up to a specific target sum.
• Use a hash map to store the difference between the target and each element as you iterate through the array.

• Example: For array [2, 7, 11, 15] and target 9, store 7 in the map when you encounter 2.

• When you find 7 later in the array, you can retrieve 2 from the map, confirming they sum to 9.

• Time complexity is O(n) due to a s...read more
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Q2. What is inheritance in oops
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Inheritance in OOP allows a class to inherit properties and behaviors from another class.
• Inheritance promotes code reusability by allowing a new class to use the properties and methods of an existing class.

• The class that is being inherited from is called the base class or parent class, while the class that inherits is called the derived class or child class.

• Derived classes can add new properties and methods, or overrid...read more
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Q1. Singleton Pattern in details
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Singleton pattern ensures a class has only one instance and provides a global point of access to it.
• Ensures a class has only one instance by providing a global access point to it.

• Uses a private constructor to restrict instantiation of the class.

• Provides a static method to access the singleton instance.

• Commonly used in scenarios where only one instance of a class is needed, such as database connections or logging.

• Exampl...read more
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Q2. Difference between POJO and Bean
Ans. 
POJO is a Plain Old Java Object with private fields and public getters/setters, while a Bean is a Java class with private fields and public zero-argument constructors.
• POJO stands for Plain Old Java Object

• POJO has private fields and public getters/setters

• Bean is a Java class with private fields and public zero-argument constructors

• Beans are usually used in Java EE frameworks like Spring for dependency injection
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Q3. Product of an array except self
Ans. 
Calculate the product of all elements in an array except for the element itself.
• Iterate through the array and calculate the product of all elements except the current element.

• Use two separate arrays to store the product of elements to the left and right of the current element.

• Multiply the corresponding elements from the left and right arrays to get the final result.
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Q1. String a = "Something" String b = new String("Something") How many object created?
Ans. 
Two objects created - one in the string pool and one in the heap.
• String 'a' is created in the string pool, while String 'b' is created in the heap.

• String pool is a special area in the heap memory where strings are stored to increase reusability and save memory.

• Using 'new' keyword always creates a new object in the heap, even if the content is the same as an existing string in the pool.
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Q2. Predict Output based on whether static variables can be accessed from non-static method
Ans. 
Static variables can be accessed from non-static methods using an object reference or by making the variable non-static.
• Static variables can be accessed from non-static methods by creating an object of the class containing the static variable.

• Alternatively, the static variable can be made non-static to be accessed directly from a non-static method.

• Attempting to access a static variable directly from a non-static method...read more
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Q3. Java 8 Features
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Q1. Write code to emulate Producer/Consumer Problem
Ans. 
Emulate Producer/Consumer Problem using code
• Create a shared buffer between producer and consumer

• Use synchronization mechanisms like mutex or semaphore to control access to the buffer

• Implement producer and consumer functions to add and remove items from the buffer respectively
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Q2. Write code to create a deadlock
Ans. 
Creating a deadlock involves two or more threads waiting for each other to release a resource they need.
• Create two threads, each trying to lock two resources in a different order

• Ensure that one thread locks resource A first and then tries to lock resource B, while the other thread locks resource B first and then tries to lock resource A

• This will result in a situation where each thread is waiting for the other to releas...read more
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Q3. Write code to implement LRU Cache
Ans. 
Implement LRU Cache using a data structure like LinkedHashMap in Java
• Use LinkedHashMap to maintain insertion order

• Override removeEldestEntry method to limit cache size

• Update the access order on get and put operations
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Q4. Write code two merge and remove duplicates from two sorted arrays with any Collections
Ans. 
Merge and remove duplicates from two sorted arrays without using Collections
• Use two pointers to iterate through both arrays simultaneously

• Compare elements at each pointer and add the smaller one to the result array

• Skip duplicates by checking if the current element is equal to the previous element
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Q5. Questions related to Java Commands used to start a java program (mvn related)
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Q6. Java Memory Model
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Q7. Write code to start 5 threads
Ans. 
Code to start 5 threads in Java
• Create a class that implements the Runnable interface

• Instantiate 5 objects of the class

• Create 5 threads using the objects and start them
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Q8. String a = "Something" a.concat(" New") What will be garbage collected?
Ans. 
Only the original string 'Something' will be garbage collected.
• The concat method in Java does not modify the original string, but instead returns a new string with the concatenated value.

• In this case, 'a' remains as 'Something' and a new string 'Something New' is created, but not assigned to any variable.

• Since the new string is not stored in any variable, it will not be garbage collected.
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Q9. Write code to read a file
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Code to read a file in Java
• Use FileReader and BufferedReader classes to read the file

• Handle exceptions using try-catch blocks

• Close the file after reading using close() method
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It is quite easy.topics like train speed and time , profit loss and work hour energy problems

Coding will be based on DSA .In depth graphs and trees would been asked

Q1. Given a question regarding patterns
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Q2. Explain about os
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An operating system (OS) is software that manages computer hardware and software resources, providing services for computer programs.
• An OS acts as an intermediary between users and the computer hardware.

• Examples of popular operating systems include Windows, macOS, and Linux.

• The OS manages system resources like CPU, memory, and storage.

• It provides a user interface, which can be command-line or graphical.

• The OS handles f...read more
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Q3. Some SQL commands
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Q4. Explain system calls
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System calls are the interface between user applications and the operating system, allowing programs to request services from the OS.
• System calls provide a way for programs to interact with the operating system.

• Common system calls include file operations (open, read, write, close).

• Examples of system calls: 'fork()' for creating processes, 'exec()' for executing programs.

• They enable resource management, such as memory a...read more
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First round was online assessment consisting of aptitude and coding questions.

Q1. First round consisted of coding 3 questions. String reversal , binary to decimal, finding index of word "golden" in given sentence.
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Q1. It involved questions related to my resume and computer networks and basics of c++.
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