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Once a constant is defined in PHP, it ______ be changed during the execution of the script.

  • Cannot
  • Can
  • Must
  • May
Once a constant is defined in PHP, it cannot be changed during the execution of the script. Constants are intended to store fixed values that remain constant throughout the execution of the script. They are not meant to be modified or redefined once defined. Any attempt to change a constant's value will result in an error. This behavior ensures the integrity and consistency of the constant values throughout the script's execution. Learn more: https://www.php.net/manual/en/language.constants.php
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You are writing a PHP script and you need to check if a variable contains a numeric value. How would you do this?

  • is_numeric($variable)
  • is_string($variable)
  • is_integer($variable)
  • is_bool($variable)
To check if a variable contains a numeric value in PHP, you can use the is_numeric() function. The is_numeric() function checks if a variable can be evaluated as a number, whether it is an integer, float, or a numeric string. It returns true if the variable is numeric and false otherwise. This function is useful when you need to validate the numeric nature of a variable. Learn more: https://www.php.net/manual/en/function.is-numeric.php
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The ________ reference data type in Java is immutable and stores a sequence of characters.

  • String
  • StringBuilder
  • List
  • Array
The String class in Java is an immutable reference data type that stores a sequence of characters. Being immutable means that once a String object is created, its content cannot be changed. Understanding the immutability of strings is crucial for efficient string manipulation in Java.
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In Java 8, the Stream API introduces the concept of stream processing, which is influenced by the ________ paradigm.

  • functional
  • imperative
  • object-oriented
  • procedural
The Stream API in Java 8 is influenced by the functional programming paradigm. Functional programming focuses on treating computation as the evaluation of mathematical functions, which aligns well with the stream processing concept in Java's Stream API.
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What will be the result of attempting to compile and run a Java class that contains a variable declared as int public;?

  • A compilation error will occur due to using a reserved keyword as a variable name.
  • The code will compile and run without errors.
  • The code will compile but result in a runtime error.
  • The code will compile but will produce a warning message.
In Java, "public" is a reserved keyword used to declare access modifiers. Using it as a variable name will result in a compilation error since you cannot use reserved keywords as variable names. This is a fundamental rule in Java's syntax. Attempting to compile and run such code will indeed lead to a compilation error.
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Imagine you are developing a multi-threaded application where threads are performing both read and write operations on shared resources. How would you ensure that the data is not corrupted without degrading performance significantly?

  • Avoid synchronization altogether and use atomic operations.
  • Implement read-write locks to allow multiple readers or a single writer.
  • Use a single global lock for all shared resources.
  • Use fine-grained locks for individual data elements.
In a multi-threaded application with both read and write operations on shared resources, using read-write locks is an effective approach. Read operations can occur concurrently, while write operations are exclusive. Fine-grained locks might lead to excessive contention and performance degradation. Using a single global lock can lead to contention, while avoiding synchronization altogether can risk data corruption.
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In a web server application where numerous HTTP requests are processed, how would you utilize ExecutorService to efficiently manage resources and handle requests?

  • Use a CachedThreadPoolExecutor: Dynamically adjust the thread pool size based on request load.
  • Use a FixedThreadPoolExecutor: Allocate a fixed number of threads to handle incoming requests efficiently.
  • Use a ScheduledThreadPoolExecutor: Schedule periodic tasks to manage resources.
  • Use a SingleThreadPoolExecutor: Process requests sequentially to ensure thread safety.
In a web server application, a FixedThreadPoolExecutor is a good choice. It allocates a fixed number of threads, ensuring resource control and efficient handling of requests. CachedThreadPoolExecutor might create too many threads, SingleThreadPoolExecutor processes sequentially, and ScheduledThreadPoolExecutor is not designed for this purpose.
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Which keyword is used in Java to test a condition?

  • check
  • if
  • test
  • verify
In Java, the if keyword is used to test a condition. It allows you to execute a block of code only if the condition specified inside the parentheses evaluates to true. The if statement is fundamental for implementing conditional logic in Java programs.
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What is the purpose of the finally block in Java exception handling?

  • To always execute code
  • To catch exceptions
  • To handle checked exceptions
  • To throw exceptions
The finally block in Java exception handling is used to ensure that a certain block of code is executed regardless of whether an exception is thrown or not. It is typically used to perform cleanup actions, such as closing resources.
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Which method can be used to temporarily pause the execution of a thread for a specified time?

  • pause()
  • sleep()
  • stop()
  • yield()
The sleep() method in Java is used to temporarily pause the execution of a thread for a specified amount of time. It's a way to introduce delays in a program and is often used for synchronization or timing purposes. The other options are not used for pausing threads in this manner.
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