What does the substring method of the String class do?
- Checks if the string is empty.
- Converts the string to lowercase.
- Retrieves the string's length.
- Returns a new string with a portion of the original string.
The substring() method of the String class in Java returns a new string that is a subset of the original string. It takes two parameters, the starting index and the ending index, and extracts the characters within that range, creating a new string. The other options do not describe the functionality of the substring() method.
In which scenarios is it recommended to create a custom exception instead of using a standard Java exception?
- When you want to avoid using exceptions altogether.
- When you want to hide error details from the caller.
- When you want to make the exception unchecked.
- When you want to provide more specific information about the error.
It is recommended to create custom exceptions when you want to provide more specific information about the error. This helps in better error handling and debugging. Custom exceptions can also encapsulate application-specific logic related to the error.
How does Java manage the memory allocation of primitive and reference data types in the stack and heap?
- Primitive data types are always allocated on the stack, and reference data types are allocated on the heap.
- Both primitive and reference data types are always allocated on the stack.
- Primitive data types are allocated on the stack, and reference data types are allocated on the heap, but the exact allocation depends on the context.
- Primitive data types are always allocated on the heap, and reference data types are allocated on the stack.
In Java, primitive data types like int, char, and boolean are typically allocated on the stack because they have fixed sizes and are stored directly in the memory location of the variable. Reference data types, such as objects, are allocated on the heap because their sizes can vary, and they need to be dynamically managed. However, it's important to note that references to objects (not the objects themselves) can be stored on the stack. The allocation of memory depends on the context and whether the reference is local or part of an object.
What does the Future interface represent in Java concurrency?
- A class for creating threads in Java
- A class for handling exceptions thrown by threads
- A class for storing past execution results
- A representation of a result that is yet to be computed
The Future interface in Java represents a result that is yet to be computed. It is used in concurrency to obtain the result of asynchronous operations. It allows you to check if the computation is complete, cancel the computation, and retrieve the result when it becomes available. This is commonly used with the Executor framework to manage concurrent tasks.
You're designing a photo gallery using a grid layout. Each row should display three images. The middle image in each row should be twice as large as the images on its sides. How would you achieve this?
- Use grid-template-areas property.
- Apply grid-row: span 2 to the middle image.
- Use grid-template-columns with explicit column sizes.
- Set grid-auto-flow: dense.
To achieve this layout, you should apply grid-row: span 2 to the middle image. This CSS rule will make the middle image span two rows, making it twice as large as the other images in the row.
In SCSS, the @import directive allows you to ________.
- Create a new CSS class
- Define variables
- Import external CSS files
- Set media queries
The @import directive in SCSS is used to import external CSS files into your SCSS code. It's a way to modularize your styles and manage them in separate files, promoting better organization and maintainability.
You want to set a global color scheme for a website using CSS variables. Where would be the best place to define these custom properties?
- In a separate CSS variables file
- In an external CSS file
- In the CSS for each individual element
- In the HTML section
To set a global color scheme for a website using CSS variables, it's best to define these custom properties in an external CSS file. This allows you to centralize your variable definitions, making it easier to maintain and update the color scheme across your entire website. While you can define CSS variables in other places like the HTML section or inline CSS for specific elements, it's not as efficient or maintainable for global color schemes.
Which CSS property is used to control the time between the end of one animation iteration and the start of the next?
- animation-delay
- animation-duration
- animation-play-state
- animation-timing-function
The animation-delay property is used to control the time between the end of one animation iteration and the start of the next. It specifies a delay before the animation begins and can be helpful for creating timed animations and controlling their sequence.
In Flexbox, how would you align all items to the center of the container both vertically and horizontally?
- Apply justify-content: center and align-items: center.
- Apply margin: auto to all flex items.
- Set display: flex; and align-content: center.
- Use text-align: center on the container element.
To align all items both vertically and horizontally in a Flexbox container, you can use justify-content: center to center items horizontally and align-items: center to center them vertically. This combination ensures that items are centered in the container along both axes.
The text-indent property in CSS is used to adjust ________.
- letter spacing
- line height
- text alignment
- the first line of a block of text
The "text-indent" property in CSS is used to adjust the indentation of the first line of a block of text. It specifies the amount by which the first line of a block-level element should be indented from the left margin.