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Java Error & Exceptions
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Java Multithreading
- Java - Multithreading
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Java Synchronization
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Java Networking
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Java Collections
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Java Data Structures
Java Collections Algorithms
Advanced Java
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Java Miscellaneous
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- Java 8 - New Features
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- Java 10 - New Features
- Java 11 - New Features
- Java 12 - New Features
- Java 13 - New Features
- Java 14 - New Features
- Java 15 - New Features
- Java 16 - New Features
Java APIs & Frameworks
Java Class References
- Java - Scanner
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Java Useful Resources
Java Online Quiz
Following quiz provides Multiple Choice Questions (MCQs) related to Core Java. You will have to read all the given answers and click over the correct answer. If you are not sure about the answer then you can check the answer using Show Answer button. You can use Next Quiz button to check new set of questions in the quiz.
Answer : B
Explaination
Objects are allocated memory in heap memory space.
Answer : B
Explaination
The short data type is represented by 16-bit signed two's complement integer.
Minimum value: -32,768
Maximum value: 32,767
Answer : B
Explaination
Short variable has default value of 0 if defined as an instance/static variable.
Q 4 - Which of the following is true about String?
Answer : B
Explaination
String object is immutable so that once it is created a String object cannot be changed. Since String is immutable it can safely be shared between many threads which are considered very important for multithreaded programming.
Q 5 - What is Encapsulation?
A - Encapsulation is a technique to define different methods of same type.
B - Encapsulation is the ability of an object to take on many forms.
Answer : C
Explaination
It is the technique of making the fields in a class private and providing access to the fields via public methods. If a field is declared private, it cannot be accessed by anyone outside the class, thereby hiding the fields within the class. Therefore encapsulation is also referred to as data hiding.
Answer : A
Explaination
Holding the reference of the other class within some other class is known as composition. It represents a HAS-A relationship. For example, a Student has a Pen. Here Student class has Pen as its instance variable.
Q 7 - What is NullPointerException?
B - A NullPointerException is thrown when object is set as null.
C - A NullPointerException is thrown when object property is set as null.
Answer : A
Explaination
A NullPointerException is thrown when calling the instance method of a null object or modifying/accessing field of a null object.
Q 8 - What happens when thread's yield() method is called?
A - Thread returns to the ready state.
Answer : A
Explaination
When a task invokes its yield() method, it returns to the ready state.
Q 9 - What is runtime polymorphism?
Answer : A
Explaination
Runtime polymorphism or dynamic method dispatch is a process in which a call to an overridden method is resolved at runtime rather than at compile-time. In this process, an overridden method is called through the reference variable of a superclass.
Q 10 - Which of the following is a thread safe?
Answer : B
Explaination
StringBuffer is thread safe.