Deutsche Telekom Interview Questions and Answers for Experienced

Q1. OOPs Concepts, like Abstraction, Polymorphism, Encapsulation etc.
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Q2. Write java program to reverse a string.
Ans. 
Java program to reverse a string
• Create a char array from the input string

• Use two pointers to swap characters from start and end of the array

• Convert the char array back to a string and return
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Q3. API error codes meanings.
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API error codes are numerical or alphanumeric codes that indicate the type of error that occurred during an API request.
• API error codes help developers identify and troubleshoot issues with their API requests.

• Common API error codes include 400 Bad Request, 401 Unauthorized, 404 Not Found, 500 Internal Server Error.

• Each API error code has a specific meaning and can provide valuable information for debugging.
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Q4. Exceptions encountered during Automation.
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Exceptions encountered during automation testing can include element not found, timeout, invalid input, etc.
• ElementNotVisibleException: When an element is present in the DOM but not visible on the page

• TimeoutException: When a command takes longer than the timeout specified

• NoSuchElementException: When an element could not be found in the DOM

• StaleElementReferenceException: When an element is no longer attached to the DOM

• ...read more
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App is taking long to process a functionality what could be the possible reasons?

Q1. Difference btwn jdk , jre and jvm
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JDK is a development kit that includes JRE and tools for developing Java applications. JRE is a runtime environment for executing Java programs. JVM is a virtual machine that runs Java bytecode.
• JDK (Java Development Kit) includes JRE (Java Runtime Environment) and development tools like compiler and debugger.

• JRE (Java Runtime Environment) is a software package that provides the libraries and components necessary for ru...read more
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Q2. Difference btwn static and volatile
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Static variables are shared among all instances of a class, while volatile variables are used to indicate that a variable's value will be modified by different threads.
• Static variables are initialized only once at the start of the program and retain their value throughout the program's execution.

• Volatile variables are used to ensure visibility of changes to variables across multiple threads.

• Static variables are accesse...read more
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Q3. What is final keyword
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Final keyword is used in Java to declare constants, prevent method overriding, and prevent class inheritance.
• Used to declare constants - value cannot be changed once assigned

• Prevents method overriding - method cannot be overridden in child classes

• Prevents class inheritance - class cannot be extended
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Q4. Difference btwn paralle stream and stream
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Parallel stream allows processing elements concurrently, while stream processes elements sequentially.
• Parallel stream can improve performance by utilizing multiple threads for processing.

• Stream processes elements one by one in a sequential manner.

• Example: stream().parallel() vs stream().sequential()
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Q5. What is stream used for
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Streams are used in Java to process collections of objects in a functional style.
• Streams allow for concise and readable code when working with collections.

• They support operations like filter, map, reduce, and collect.

• Streams can be sequential or parallel, depending on the processing requirements.

• Example: List<String> names = Arrays.asList("Alice", "Bob", "Charlie"); names.stream().filter(name -> name.startsWith("...read more
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Q1. Angular Structure
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Q2. What are interceptor in angular
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Interceptors in Angular are services that allow you to intercept and modify HTTP requests and responses.
• Interceptors implement the HttpInterceptor interface.

• They can modify request headers, handle errors, and log requests.

• Example: Adding an authorization token to every request.

• Interceptors can also transform responses before they reach the component.

• They are registered in the AppModule using the HTTP_INTERCEPTORS provi...read more
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Q1. Implement stack using linkedlist, discussion on singleton design pattern, java output question
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Q1. Hashmap Implementation, discussion on arraylist,hashmap, concurrent hashmap, one coding question on string , some other basisc java topic discussed
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Q1. Sample spring boot code from scratch, discussed all used annotations, exceptional handling, spring security, discussion on complexity of some data structure
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