Java Methods and Classes Quiz
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Questions and Answers

What happens when two threads access the same ArrayList object simultaneously?

  • A ConcurrentModificationException is thrown (correct)
  • One thread accesses the object, causing the other to be blocked
  • Both threads can access the object without any issue
  • Both threads receive a Null Pointer exception

    • Which method in the Date class checks if a date occurs before a specified date?

  • isBefore()
  • precedes()
  • before() (correct)
  • compare()

    • Which class is used to associate a value with a String key in Java?

  • Properties (correct)
  • Map
  • Dictionary
  • Hashtable

    • What is the primary role of packages in Java?

    <p>To group classes and interfaces</p> Signup and view all the answers

    Which keyword is used in Java to declare a package?

    <p>package</p> Signup and view all the answers

    When utilizing the Breadth First Traversal algorithm in graph theory, which data structure is primarily used?

    <p>Queue</p> Signup and view all the answers

    What will be the output of the provided Java program that adds 'A' and then 'B' at index 0 in an ArrayList?

    <p>2</p> Signup and view all the answers

    Can a Java package contain other sub-packages?

    <p>Yes, packages can have sub-packages</p> Signup and view all the answers

    How do you correctly import a package in Java?

    <p>import packageName;</p> Signup and view all the answers

    Which of the following is NOT a method for manipulating data in a Java Array?

    <p>insert()</p> Signup and view all the answers

    What is the outcome when a thread is paused by another thread of the same priority?

    <p>It pauses the thread to allow other threads of the same priority to execute.</p> Signup and view all the answers

    What type of exception is specifically thrown when the sleep() method is interrupted?

    <p>InterruptedException</p> Signup and view all the answers

    What functionality does the notifyAll() method provide in terms of thread coordination?

    <p>Wakes up all waiting threads on the object's monitor.</p> Signup and view all the answers

    Which of the following is the primary method used to create a thread pool in Java?

    <p>Executors</p> Signup and view all the answers

    What is the most significant advantage of utilizing thread pools in Java applications?

    <p>Improved control over thread life cycles and resource allocation.</p> Signup and view all the answers

    How can a daemon thread be characterized in Java?

    <p>A thread that supports background operations.</p> Signup and view all the answers

    Which method would you call to determine if the current thread is designated as a daemon thread?

    <p>isDaemon()</p> Signup and view all the answers

    In Java, which class embodies the concept of a monitor for synchronization purposes?

    <p>Object</p> Signup and view all the answers

    In evaluating thread execution, what will happen to a paused thread when notified?

    <p>It will either resume or remain paused based on priority.</p> Signup and view all the answers

    What happens to a non-daemon thread when all daemon threads are completed?

    <p>The non-daemon thread continues to run.</p> Signup and view all the answers

    Which method is responsible for creating a new thread from a class that extends the Thread class?

    <p>start()</p> Signup and view all the answers

    What will occur when the sleep() method is called on a thread?

    <p>The thread releases CPU but retains any locks it holds.</p> Signup and view all the answers

    Which keyword ensures that a method can only be accessed by one thread at a time?

    <p>synchronized</p> Signup and view all the answers

    What is the main purpose of the java.sql package in Java?

    <p>Engaging in database operations.</p> Signup and view all the answers

    What happens if a thread calls the run() method directly rather than using start()?

    <p>The current thread will execute the run() method.</p> Signup and view all the answers

    Which package is primarily responsible for input and output operations in Java?

    <p>java.io</p> Signup and view all the answers

    Can multiple packages in Java contain classes with the same name?

    <p>Yes, this is allowed.</p> Signup and view all the answers

    What is the result of using the deprecated stop() method to stop a thread?

    <p>It may leave shared resources in an inconsistent state.</p> Signup and view all the answers

    Which of the following describes the term 'fully qualified name' in Java?

    <p>Package name followed by class name.</p> Signup and view all the answers

    To make one thread wait for another thread's completion, which method is used?

    <p>join()</p> Signup and view all the answers

    Study Notes

    Java Methods and Classes

    • clear() method: Used to make all bits in a bit set zero.
    • Date class's before() method: Used to check if a Date object is before a specified date.
    • Properties class: Stores values using strings as keys.
    • ArrayList thread safety: Accessing the same ArrayList object by multiple threads results in a ConcurrentModificationException.
    • Adding elements to ArrayList: Adding "B" at index 0 then "A" to an empty ArrayList results in an ArrayList size of 2.
    • Breadth-First Traversal: Uses a Queue data structure.
    • Java Collection Framework Classes: Array, Stack, Queue are part of the collection framework; Maps are not.

    Packages in Java

    • Package Definition: package packageName; declares a package.
    • Package Purpose: Packages organize classes and interfaces, prevent naming conflicts, and provide access control.
    • Importing Packages: Use import packageName; or import packageName.*; to import a package or all classes from a package.
    • Fully Qualified Name: The fully qualified name is the package name followed by the class name.
    • Common Packages: java.lang is automatically imported, java.util (contains Scanner and ArrayList), java.io (input/output), java.net (networking), java.sql (database).
    • Subpackages: Packages can contain sub-packages.
    • Java Standard Library: java.util and java.io are part of the Java library. java.graphics is not part.

    Multithreading in Java

    • Starting a Thread: Use start(), not run().
    • Thread Priority: Default thread priority is 5.
    • Thread Creation: Implement the Runnable interface or extend the Thread class.
    • Thread States: States include running, waiting, blocked, and ready.
    • Thread Termination: Avoid using stop(), choose other methods to signal termination.
    • Synchronization: synchronized keyword prevents thread interference.
    • Thread Pools: Executors are used to create thread pools for better resource management and thread control.
    • Daemon Threads: Daemon threads run in the background.
    • Thread.sleep(): Pauses the thread temporarily, releasing the CPU while holding any locks.
    • join() Method: Makes one thread wait for another thread to finish.
    • Checking Thread Status: Use isAlive() to check if a thread is currently active.
    • yield() Method: Allows other threads with the same priority to execute.
    • Exceptions: InterruptedException is thrown if an interrupted thread waits for sleep to complete.
    • notifyAll() Method: Wakes up all waiting threads for an object's access.

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    Description

    Test your knowledge on essential Java methods and classes, including collections, package definitions, and traversal techniques. This quiz covers key concepts such as the ArrayList, Date class, and Properties class functions. Explore how these elements interact within the Java programming environment.

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