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Junior Java Developer Interview Questions

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3,830 junior java developer interview questions shared by candidates

1) comparator vs comparable 2) autoboxing vs unboxing 3) what is a wrapper class? how do convert Integer to int and vice versa 4) sorting algorithms and complexities 5) List vs ArrayList 6) List vs Set 7) TreeSet vs HashSet 8) Which set can we use to maintain the order of elements 9) ArrayList vs Array 10) what is hashcode and equals functions 11) equals() vs == 12) what is exception handling in Java 13) What is the rule to follow, when we have multiple catches blocks to write? (regarding the order or catch classes) 13) singleton pattern in Java 14) 2 threads are trying to access a singleton object at the same, how do you handle 15) Multiple inheritance in Java 16) 4 pillars of OOPS explain with example 17) overloading vs overriding - example 18) what are access specifiers in Java 19) can protected data be accessed by any other classes other than a subclass 20) Interface vs abstract class 21) what is a servlet? what is spring and spring boot 22) Any experience implementing REST API? 23) Did you ever fetch data from database 24) Describe any challenging task you have worked on or a recent interesting work 25) DSA Implementation : write java code to Merge 2 sorted arrays
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Junior Java Developer

Interviewed at Xebia

3.8★
Jul 3, 2024

1) comparator vs comparable 2) autoboxing vs unboxing 3) what is a wrapper class? how do convert Integer to int and vice versa 4) sorting algorithms and complexities 5) List vs ArrayList 6) List vs Set 7) TreeSet vs HashSet 8) Which set can we use to maintain the order of elements 9) ArrayList vs Array 10) what is hashcode and equals functions 11) equals() vs == 12) what is exception handling in Java 13) What is the rule to follow, when we have multiple catches blocks to write? (regarding the order or catch classes) 13) singleton pattern in Java 14) 2 threads are trying to access a singleton object at the same, how do you handle 15) Multiple inheritance in Java 16) 4 pillars of OOPS explain with example 17) overloading vs overriding - example 18) what are access specifiers in Java 19) can protected data be accessed by any other classes other than a subclass 20) Interface vs abstract class 21) what is a servlet? what is spring and spring boot 22) Any experience implementing REST API? 23) Did you ever fetch data from database 24) Describe any challenging task you have worked on or a recent interesting work 25) DSA Implementation : write java code to Merge 2 sorted arrays

Do you know OOPS concept? Suppose you have an Employee class and you want to use it key. Then what changes you need to do? How will you manage collison? In spring boot application, why Main class(containing main() method is at the root package? Explain SpringBootApplication annotation. What is spring security? Write code to demonstrate runtime poymorphism.
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Junior Java Developer

Interviewed at Wissen

3.9★
Jul 30, 2025

Do you know OOPS concept? Suppose you have an Employee class and you want to use it key. Then what changes you need to do? How will you manage collison? In spring boot application, why Main class(containing main() method is at the root package? Explain SpringBootApplication annotation. What is spring security? Write code to demonstrate runtime poymorphism.

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