Hi all, below are the questions asked in paytm interview for 2yr experienced guy in java technology. I could remember these much only, although there were more questions.
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Round 1:
- Explained previous projects.
- Interfaces vs abstract class
interface i1 : void fun()
interface i2 : int fun()
interface i3 : Object fun(int x)
class implementing all these interfaces has to implement all methods or one?interface i1 : void fun()
interface i2 : void fun()
interface i3 : void fun()
now what will be the behavior if a class implement all interfaces? - Given m*n matrix containing 0s and 1s in sorted order. count the row with a maximum number of 1s.
- Given a rod of length d. there is a price associated with every piece of rod. the buyer wishes to buy a rod of length n where there can be any number of cuts in it. find the no. of cuts required to get rod of length n with minimum cost to be paid.
- Last question of the round with a choice to attempt only 1.
- Given 8 balls out of which 1 is unequal. find it in a minimum number of comparisons.
or - Given some integers. there can be only 3 operations to be performed on the integers i.e., add, subtract and concat. find minimum no. of operations to get number x (100).
- Given 8 balls out of which 1 is unequal. find it in a minimum number of comparisons.
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Round 2:
- Static synchronized and synchronized method, will both of them executed parallelly if called by different threads at the same time?
- Set, hashmap implementations, linkedhashmap how it works. what is the threshold value of hashmap, load factor?
- How to resize happens in hashmap.
- When java structures the linked list entry buckets in a hashmap to tree? what kind of tree does it maintain? avl or rbtree?
- What are the properties of the two trees?
- Remote method invokation (rmi), socket?
- Find nth largest from stream of integers. Hint: use partition algo to identify nth largest, loop till pivot is not equal to n.
- C: what does printf return? what does scanf return?
- Optimistic locking.
- Thread pool executor. concurrent packages.
- What is hibernate? why do we use it?
- spring ioc, di.
- Design patterns.
- Given a 2-d plane with 3 coordinates which forms a triangle. given a point tell whether it is present inside triangle or not.
- Thread states? difference between blocked and waiting state?
- Java is pass by value or pass by reference?
- Asked about previous projects.
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Round 3:
- Design a car parking system. there are slots, return the best slot for vehicle arrived, APIs, DB, classes etc. Also telling best slot should be less than o(n).
- What all interfaces are there in collections? their implementations?
- Stack queue in what package?
- Singleton class, what if two threads access singleton at same time, what if constructor made accessible by reflection?
- Asked about previous projects.
- Heap implementations.
- Implement arraylist using a data structure.
- Heapsort methods with each taking how much time?
Didn’t got selected, attitude of the interviewers was like whatever they asked has to be answered and are god as know more than you. Although it taught a lot in the end.
Best of luck 🙂