10+ Java Developer Trainee Interview Questions and Answers for Freshers

Find the lowest number from an arraylist using streams

• Use stream.min() method to find the lowest number

• Pass Comparator.naturalOrder() to get the lowest number

• Handle empty list scenario using OptionalInt

Create two objects based on user input using control flow statements in Java.

• Use Scanner class to take user input

• Use if-else or switch statements to create objects based on input

• Instantiate objects with appropriate constructors

Map is an interface in Java that maps unique keys to values.

• Map is a part of the Java Collections Framework

• It is used to store key-value pairs

• Some common implementations of Map are HashMap, TreeMap, and LinkedHashMap

Inheritance in Java allows a class to inherit properties and methods from another class.

• Use the 'extends' keyword to create a subclass that inherits from a superclass

• The subclass can access all public and protected members of the superclass

• Example: class Dog extends Animal { ... }

• The 'super' keyword is used to call the superclass constructor or method

Abstract classes are incomplete classes that cannot be instantiated. Anonymous classes are unnamed classes that can be created on the fly.

• Abstract classes are declared with the 'abstract' keyword and can have abstract and non-abstract methods.

• Anonymous classes are created using the 'new' keyword and can extend a class or implement an interface.

• Anonymous classes are often used for event handling and callbacks.

• Example of abstract class: abstract class Shape { abstract void draw...read more

Program to find duplicate alphabets in a string

• Create a HashMap to store the frequency of each alphabet

• Iterate through the string and update the frequency in the HashMap

• Iterate through the HashMap and print the alphabets with frequency greater than 1

Reverse a given string

• Iterate through the string from end to start and append each character to a new string

• Use StringBuilder or StringBuffer for better performance

• Convert the string to a character array and swap the first and last characters, then move towards the middle until the entire string is reversed

Controller in Spring is responsible for handling user requests and returning appropriate responses.

• Controller receives requests from the client and delegates them to appropriate handlers

• It maps the incoming requests to the corresponding handler methods

• It returns the response to the client after processing the request

• It can also handle exceptions and errors that occur during request processing

Merging two arrays of strings in Java.

• Create a new array with size equal to the sum of sizes of both arrays.

• Copy elements of first array to the new array.

• Copy elements of second array to the new array starting from the end of first array.

• Return the new array.

Refresh scope is used in Spring framework to control the lifecycle of beans.

• Refresh scope is used to create a new instance of a bean every time it is requested.

• It is useful when the state of a bean needs to be reset on every request.

• To use refresh scope, add @RefreshScope annotation to the bean definition.

• Example: @Bean @RefreshScope public MyBean myBean() { return new MyBean(); }