The ________ class represents a Uniform Resource Identifier and is designed to handle the complete URI syntax.
- URI
- URL
- URN
- UniformResource
The correct answer is "URI." In Java, the URI class is used to represent a Uniform Resource Identifier. It's designed to handle the complete URI syntax, including components like scheme, authority, path, query, and fragment. A URI is a broader concept that includes URLs (Uniform Resource Locators) and URNs (Uniform Resource Names).
The ________ method of the ExecutorService interface is commonly used to submit a Callable task and returns a Future object.
- execute
- invokeAll
- start
- submit
In Java, the submit method of the ExecutorService interface is used to submit a Callable task and returns a Future object representing the result of the computation. This method is commonly used for asynchronous tasks that return results.
A constructor in Java cannot have a return type and is declared with the same name as the ________.
- class
- interface
- method
- object
In Java, constructors are special methods used to initialize objects. They have the same name as the class they belong to, making option 1 ("class") the correct choice. Constructors cannot have a return type.
The ______ arithmetic operator divides the left-hand operand by the right-hand operand and returns the remainder.
- %
- *
- +
- -
The "%" (modulo) operator in Java is used to divide the left-hand operand by the right-hand operand and returns the remainder. For example, "10 % 3" returns 1 because 10 divided by 3 leaves a remainder of 1. The other operators perform different arithmetic operations.
What is the initial capacity of the HashMap when no size is defined, and how is it related to the number of entries it can ideally accommodate without resizing?
- 16, and it can accommodate 16 entries.
- 10, and it can accommodate 10 entries.
- 32, and it can accommodate 32 entries.
- The initial capacity is not defined, and it dynamically adjusts as entries are added.
In Java, when you create a HashMap without specifying an initial capacity, it defaults to an initial capacity of 16. This means that initially, the HashMap can accommodate 16 key-value pairs. However, as the number of entries increases and reaches a certain threshold (usually 75% of the capacity), the HashMap automatically resizes itself, doubling its capacity. So, option (a) is correct, with the explanation that it can ideally accommodate 16 entries initially but will resize when necessary.
What will be the output of calling a method overridden in the child class?
- It depends on how the method is called
- It depends on the method's signature
- The child class's method will always be called
- The parent class's method will always be called
When a method is overridden in the child class, the version of the method in the child class is called when the method is invoked on an instance of the child class. This is known as method overriding and is a fundamental concept in object-oriented programming.
How does the compiler resolve the "+" operator when used with different data types (e.g., String and int)?
- It performs the operation based on the type of the first operand and ignores the second operand's type.
- It throws a compilation error because the + operator cannot be used with different data types.
- It throws a runtime error because the + operator is ambiguous with different data types.
- It uses type conversion to promote one of the operands to the type of the other operand, and then performs the operation.
It uses type conversion to promote one of the operands to the type of the other operand, and then performs the operation. For example, if you add a string and an int, the int is converted to a string, and string concatenation is performed. If you add two integers, normal addition is performed.
Imagine you are developing a text editor that frequently alters strings (like undo, redo, replace, cut, copy, and paste operations). Which class(es) would you utilize for efficient memory and performance management?
- String and PhantomReference
- StringBuffer and SoftReference
- StringBuilder and WeakReference
- StringJoiner and ReferenceQueue
In a text editor, where efficient memory and performance management are crucial, StringBuilder is used for in-place string manipulation, and WeakReference helps in memory management by allowing objects to be garbage collected when not strongly referenced. StringBuffer is thread-safe but may not provide the best performance. The other options are not suitable for such scenarios.
What happens when the join() method is called on a thread?
- The calling thread will wait for the specified thread to finish.
- The specified thread will be paused but continue executing later.
- The specified thread will be terminated immediately.
- The specified thread will wait for the calling thread to finish.
When the join() method is called on a thread in Java, the calling thread will wait for the specified thread to finish its execution. This is often used to ensure that a thread completes its task before the calling thread proceeds. It's a mechanism for thread synchronization.
How does type inference work with Lambda expressions in Java?
- Type inference always uses the Object type for Lambda parameters.
- Type inference automatically infers parameter types from the context and Lambda body.
- Type inference is not applicable to Lambda expressions in Java.
- Type inference relies on explicit type declarations for Lambda parameters.
In Java, Lambda expressions benefit from type inference, which allows the compiler to automatically infer the parameter types from the context and the Lambda body. This feature makes Lambda expressions concise and expressive. It helps reduce the verbosity of code by eliminating the need for explicit type declarations in most cases. Understanding how type inference works with Lambdas is essential for writing clean and readable code when using functional programming techniques in Java.