Infosystems Java Developer Interview Questions and Answers

Q1. They asked some core Java Concepts,String,Java 8,SpringBoot Architecture,Stream API code
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Q1. Java 8 features
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Q2. Junit code writing
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Q1. Reason for job change
Ans. 
Seeking new challenges and growth opportunities in a dynamic environment.
• Desire for professional growth

• Seeking new challenges

• Interested in a more dynamic work environment
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Q2. Past experience
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Q1. Ask to write code for equal and hashcode in notepad
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Q2. Type of Collections and its internal working
Ans. 
Java collections are data structures that store and manipulate groups of objects.
• Types of collections include List, Set, Map, Queue, etc.

• Internal workings involve data structures like arrays, linked lists, hash tables, etc.

• Collections framework provides interfaces and classes for working with collections.
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Q3. Count number of occurrence of string from Array
Ans. 
Count occurrences of a specific string in an array of strings.
• Iterate through the array and use a HashMap to store the count of each string.

• Use the string as key and increment the count each time it is encountered.

• Return the count of the specific string at the end.
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Q4. Write a code using stream
Ans. 
Using stream to filter a list of strings
• Use the filter method to apply a predicate to each element in the stream

• Convert the stream back to a list using the collect method
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Q1. Cycle sort based question
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Q2. Streams api, optional, lambda implementation
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Q3. Hashmap iteration ways
Ans. 
There are multiple ways to iterate over a HashMap in Java.
• Using keySet() and values() methods

• Using entrySet() method

• Using forEach() method with lambda expression
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Q4. Method overriding based code question -> guess the output
Ans. 
Method overriding in Java with code example
• Output will be 'Child class method' as the method in Child class overrides the method in Parent class

• Method overriding is a feature that allows a subclass to provide a specific implementation of a method that is already provided by its superclass

• The method in the subclass should have the same name, return type, and parameters as the method in the superclass
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Q5. Write API to save data
Ans. 
API to save data in Java
• Use HTTP POST method to send data to the server

• Create a RESTful endpoint to handle the data saving

• Validate the input data before saving it to the database
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Q1. Microservices communication
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Q2. Hash map working
Ans. 
Hash map is a data structure that stores key-value pairs and allows for fast retrieval of values based on keys.
• Hash map uses hashing to map keys to their corresponding values.

• It allows for constant time complexity O(1) for insertion, deletion, and retrieval operations.

• Example: HashMap map = new HashMap<>(); map.put("key", 123); int value = map.get("key");
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Q1. Count duplicate from int array
Ans. 
Count duplicates in an int array
• Create a HashMap to store the count of each element in the array

• Iterate through the array and update the count in the HashMap

• Count the elements with count greater than 1 as duplicates
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Q1. Ask to write code for equal and hashcode in notepad
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Q2. Type of Collections and its internal working
Ans. 
Java collections are data structures that store and manipulate groups of objects.
• Types of collections include List, Set, Map, Queue, etc.

• Internal workings involve data structures like arrays, linked lists, hash tables, etc.

• Collections framework provides interfaces and classes for working with collections.

• Example: ArrayList internally uses an array to store elements.
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Q3. Count number of occurrence of string from Array
Ans. 
Count occurrences of a specific string in an array of strings.
• Iterate through the array and compare each element with the target string.

• Increment a counter each time the target string is found.

• Return the final count of occurrences.
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Q1. Java 8 feature & java 9
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Q2. Profiler concept internal work
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Separate 0 and 1 and then store in the sme array