Tag: java
Questions Related to java
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You must have a reference to an instance of the enclosing class in order to instantiate it.
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It does not have access to nonstatic members of the enclosing class.
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It's variables and methods must be static.
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It must extend the enclosing class.
To answer this question, you need to have an understanding of nested classes in Java.
A static nested class is a class that is defined inside another class, and it is marked as static. Here is an explanation of each option:
A. You must have a reference to an instance of the enclosing class in order to instantiate it. This statement is false. Unlike an inner class, a static nested class does not require an instance of the enclosing class to be instantiated. You can create an instance of a static nested class without having an instance of the enclosing class.
B. It does not have access to nonstatic members of the enclosing class. This statement is true. Since a static nested class is static, it does not have access to nonstatic members (variables or methods) of the enclosing class. It can only access static members of the enclosing class.
C. Its variables and methods must be static. This statement is false. Although the static nested class is static, it can have both static and nonstatic variables and methods. It is not required for all of its members to be static.
D. It must extend the enclosing class. This statement is false. A static nested class does not have to extend the enclosing class. It is a separate class and can have its own inheritance hierarchy.
Based on the explanations above, the correct statement about a static nested class is:
The Answer is: B. It does not have access to nonstatic members of the enclosing class.
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Runnable r = new Runnable() { };
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Runnable r = new Runnable(public void run() { });
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Runnable r = new Runnable { public void run(){}};
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System.out.println(new Runnable() {public void run() { }});
What is the name of the method used to start a thread execution?
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init();
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start();
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run();
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resume();
The start() method causes this thread to begin execution; the Java Virtual Machine calls the run method of this thread.
Which cannot directly cause a thread to stop executing?
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Calling the SetPriority() method on a Thread object.
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Calling the wait() method on an object.
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Calling notify() method on an object.
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Calling read() method on an InputStream object.
notify() - wakes up a single thread that is waiting on this object's monitor.
Which of the following will directly stop the execution of a Thread?
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wait()
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notify()
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notifyall()
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exits synchronized code
AI Explanation
To answer this question, we need to understand the concepts of thread synchronization and the methods wait(), notify(), and notifyAll().
Option A) wait() - This option is correct. The wait() method is used to suspend the execution of a thread and releases the lock it holds. It allows other threads to acquire the lock and continue their execution. The thread will remain in a suspended state until another thread calls the notify() or notifyAll() method.
Option B) notify() - This option is incorrect. The notify() method is used to wake up a single thread that is waiting on the same object. It does not stop the execution of a thread, but rather notifies one waiting thread to resume execution.
Option C) notifyAll() - This option is incorrect. The notifyAll() method is used to wake up all threads that are waiting on the same object. It also does not stop the execution of a thread but rather notifies all waiting threads to resume execution.
Option D) exits synchronized code - This option is incorrect. Exiting synchronized code does not directly stop the execution of a thread. It simply releases the lock it holds and allows other threads to acquire the lock and continue their execution.
Therefore, the correct answer is option A) wait(). This option directly stops the execution of a thread by suspending it until another thread calls the notify() or notifyAll() method.
Please let me know if you need any further clarification.
Which method must be defined by a class implementing the java.lang.Runnable interface?
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void run()
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public void run()
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public void start()
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void run(int priority)
AI Explanation
To answer this question, you need to understand the java.lang.Runnable interface.
The java.lang.Runnable interface is used to define a task that can be executed by a thread. It contains only one method that must be implemented by any class that implements this interface.
The method that must be defined by a class implementing the java.lang.Runnable interface is:
Option B) public void run()
This method represents the task that will be executed when a thread is started. It does not take any arguments and does not return any value. The implementation of this method should contain the code that defines the task to be performed by the thread.
Option A) void run() - This option is incorrect because the run() method must be defined as public when implementing the java.lang.Runnable interface.
Option C) public void start() - This option is incorrect because the start() method is not part of the java.lang.Runnable interface. The start() method is a method of the Thread class, which is used to start a new thread.
Option D) void run(int priority) - This option is incorrect because the run() method in the java.lang.Runnable interface does not take any arguments.
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run();
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start();
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stop();
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main();
Which method registers a thread in a thread scheduler?
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run();
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construct();
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start();
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register();
AI Explanation
To answer this question, you need to understand how threads are registered in a thread scheduler.
Option A) run() - This option is incorrect because the run() method is responsible for the code that will be executed when the thread is started, but it does not register the thread in the thread scheduler.
Option B) construct() - This option is incorrect because there is no specific method named construct() for registering a thread in a thread scheduler.
Option C) start() - This option is correct because the start() method is used to register a thread in a thread scheduler. When the start() method is called, the thread is added to the thread scheduler's queue and will be executed by the scheduler when its turn comes.
Option D) register() - This option is incorrect because there is no specific method named register() for registering a thread in a thread scheduler.
The correct answer is C) start(). This option is correct because the start() method is used to register a thread in a thread scheduler.
Which of the following will not directly cause a thread to stop?
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notify()
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wait()
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InputStream access
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sleep()
Which class or interface defines the wait(), notify(),and notifyAll() methods?
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Object
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Thread
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Runnable
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Class
AI Explanation
To answer this question, you need to understand the concept of multi-threading in Java. The wait(), notify(), and notifyAll() methods are used for inter-thread communication and are defined in the Object class.
Let's go through each option to understand why it is correct or incorrect:
Option A) Object - This option is correct because the wait(), notify(), and notifyAll() methods are defined in the Object class. Every class in Java is a subclass of the Object class, and therefore, these methods are available in all classes.
Option B) Thread - This option is incorrect because the Thread class is responsible for creating and managing threads, but it does not define the wait(), notify(), and notifyAll() methods.
Option C) Runnable - This option is incorrect because the Runnable interface is used to define a task that can be executed by a thread. It does not define the wait(), notify(), and notifyAll() methods.
Option D) Class - This option is incorrect because the Class class is used to represent classes and interfaces in Java. It does not define the wait(), notify(), and notifyAll() methods.
The correct answer is Option A) Object. This option is correct because the wait(), notify(), and notifyAll() methods are defined in the Object class.
Therefore, the correct answer is Option A) Object.