Deutsche Telekom Interview Questions, Process, and Tips

Q1. What did you do until now?
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Q2. What did you study?
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Q3. Can you share your experiences with mobile devices?
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Basic leetcode questions, easy to medium level.

Java concepts, OOPS, puzzles

Q1. Basic behaviour related questions.
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Q1. Java basics, automation basics.
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Q1. Find all the permutation of the Array?
Ans. 
Permutations of an array of strings are all possible arrangements of the elements.
• Use recursion to generate all permutations.

• Swap elements to create different permutations.

• Base case: when only one element is left, add the permutation to the result.

• Example: Array ['A', 'B', 'C'] has permutations ['ABC', 'ACB', 'BAC', 'BCA', 'CBA', 'CAB'].
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Q2. Find the largest number in an Array without DS and loop in Java 8?
Ans. 
Use Java 8 Stream API to find the largest number in an array of strings without using additional data structures or loops.
• Convert the array of strings to a stream of integers using map() and parseInt()

• Use reduce() with Math::max to find the largest number in the stream
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Q1. About Mobile testing
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Q1. Difference btwn jdk , jre and jvm
Ans. 
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
Ans. 
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
Ans. 
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
Ans. 
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
Ans. 
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 names = Arrays.asList("Alice", "Bob", "Charlie"); names.stream().filter(name -> name.startsWith("A")).forEach(S
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