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Java Basics

1/25 In Java, which of the following is a correct way to create a thread?
- Implementing the Runnable interface
- Extending the Thread class
- Extending the Runnable interface
- Implementing the Thread class
2/25 Which collection class in Java is synchronized?
- ArrayList
- LinkedList
- Vector
- HashSet
3/25 Which interface in Java is used for sorting and ordering?
- List
- Set
- Comparable
- Comparator
4/25 What does the 'static' keyword in Java signify?
- The method can be called without creating an instance of the class
- The method is immutable
- The method is synchronized
- The method returns a static value
5/25 Which exception is thrown when trying to access an element with a key that does not exist in a HashMap?
- NullPointerException
- ArrayIndexOutOfBoundsException
- KeyNotFoundException
- NoSuchElementException
6/25 In Java, what does the 'volatile' keyword do to a variable?
- It ensures the variable is synchronized across threads
- It makes the variable immutable
- It increases the variable's access speed
- It makes the variable transient
7/25 Which of these is an immutable class in Java?
- java.lang.StringBuilder
- java.lang.String
- java.lang.StringBuffer
- java.util.ArrayList
8/25 How do you declare a constant variable in Java?
- Using the 'constant' keyword
- Using the 'static final' keywords
- Using the 'immutable' keyword
- Declaring without initialization
9/25 What is the role of the 'break' statement in a loop in Java?
- To skip the current iteration of the loop
- To pause the loop execution temporarily
- To terminate the loop immediately
- To continue loop execution indefinitely
10/25 Which of the following is a checked exception in Java?
- NullPointerException
- ArrayIndexOutOfBoundsException
- IOException
- RuntimeException
11/25 What is the purpose of the 'instanceof' operator in Java?
- To compare the performance of two objects
- To determine if a specific object is an instance of a class, superclass, or interface
- To instantiate a new object of a class
- To check the equality of two objects
12/25 What does the 'synchronized' keyword ensure in a multi-threaded environment?
- Faster execution of threads
- That only a single thread can access the method or block at a time
- That multiple threads can execute the method concurrently
- That the method will always be executed by the main thread
13/25 In Java, which method you must override to use an object as a key in a HashMap?
- hashKey()
- mapKey()
- equals() and hashCode()
- getKey()
14/25 In Java, what is the effect of assigning a 'null' value to a reference variable?
- The reference variable is deleted
- It causes a compile-time error
- The reference variable points to no object
- It automatically initializes the object
15/25 What is 'garbage collection' in Java?
- A process of deallocating memory by manually deleting objects
- A process of automatically freeing memory occupied by objects that are no longer in use
- A tool for optimizing Java code
- A method for storing unused objects
16/25 What is the difference between 'static' and 'non-static' methods in Java?
- Static methods can be called without creating an instance of the class
- Non-static methods are always synchronized
- Static methods are faster
- Non-static methods can access any class variable
17/25 In Java, what is the default layout manager for the JFrame container?
- FlowLayout
- GridLayout
- BorderLayout
- CardLayout
18/25 How can you achieve thread safety in Java?
- By using synchronized blocks or methods
- By avoiding the use of multiple threads
- By using the 'volatile' keyword
- By making all methods and variables private
19/25 What is 'JDBC' in Java?
- Java Database Connectivity, a standard API for database access
- Java Data Binding Code, a framework for binding data to UI elements
- Just-in-time Database Compiler, a tool for database optimization
- Java Deployment and Compilation, a deployment tool
20/25 What is 'encapsulation' in Java?
- The technique of wrapping code and data together into a single unit
- A process of linking a method with an object
- A method of improving code execution time
- The division of a program into smaller parts
21/25 What is 'polymorphism' in the context of Java?
- The ability of a variable to hold objects of different types
- The ability of Java to run on different platforms without modification
- The ability of a method to perform different tasks based on the object
- Changing the behavior of an object at runtime
22/25 In Java, what is the purpose of the 'enum' keyword?
- To define a new exception type
- To declare a collection of constants
- To create an enumeration of values for iteration
- To optimize memory usage in large applications
23/25 In Java, which method would you use to compare two String objects for content equality?
- compareTo()
- equals()
- match()
- equalContent()
24/25 In Java, what is the default value of a boolean variable in a class?
- true
- false
- null
- 0
25/25 What is 'type casting' in Java?
- Changing a variable from one type to another
- A method of error handling
- A process of making a class adhere to a specific interface
- Assigning a new value to a variable
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