A HashMap in Java is a data structure that provides fast access to data through key-value pairs. It works by using a hash table to store the pairs, where each key is hashed to generate an index in an array, called a bucket. Here's a brief overview of its functioning: Hashing: When a key-value pair iRead more
A HashMap in Java is a data structure that provides fast access to data through key-value pairs. It works by using a hash table to store the pairs, where each key is hashed to generate an index in an array, called a bucket. Here’s a brief overview of its functioning:
- Hashing: When a key-value pair is added to the HashMap, the key is passed through a hash function to compute a hash code. This hash code is then used to determine the index of the bucket where the pair should be stored.
- Buckets: Each index in the array corresponds to a bucket, which can store multiple key-value pairs in case of hash collisions. Initially, the array is sparse, but as more pairs are added, it may be resized and rehashed.
- Handling Collisions: HashMap handles collisions using chaining. When multiple keys hash to the same index, they are stored in a linked list (or a balanced tree if the list gets too long) within the bucket. This ensures that the structure can handle collisions efficiently.
- Operations:
- Insertion: The key is hashed, and the pair is placed in the appropriate bucket.
- Retrieval: The key is hashed, and the corresponding bucket is searched for the key.
- Deletion: The key is hashed, the bucket is located, and the key-value pair is removed.
This structure allows for average-time complexity of O(1) for insertion, deletion, and retrieval operations, making HashMap a highly efficient and widely used data structure in Java.
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In Java, functional interfaces are a central feature introduced in Java 8 to support functional programming. A functional interface is an interface with exactly one abstract method, which makes it compatible with lambda expressions. These interfaces provide target types for lambda expressions and meRead more
In Java, functional interfaces are a central feature introduced in Java 8 to support functional programming. A functional interface is an interface with exactly one abstract method, which makes it compatible with lambda expressions. These interfaces provide target types for lambda expressions and method references, allowing for more concise and readable code.
The `java.util.function` package contains several commonly used functional interfaces. Some key examples include:
1. **Predicate<T>**: Represents a boolean-valued function of one argument, typically used for filtering or matching conditions.
2. Function<T, R>: Represents a function that accepts one argument and produces a result, useful for transforming data.
3. Consumer<T>: Represents an operation that accepts a single input argument and returns no result, often used for operations like printing or logging.
4. Supplier<T>: Represents a supplier of results, providing a method to generate values without taking any arguments.
5.UnaryOperator<T> andBinaryOperator<T>: Specializations of `Function` for cases where the input and output types are the same, often used for operations like incrementing a number.
Functional interfaces enable functional programming patterns in Java, encouraging a more declarative style and facilitating parallel processing by enabling developers to pass behaviors (lambda expressions) as parameters, thereby increasing the expressiveness and flexibility of the code. This makes Java more versatile for both sequential and parallel processing.
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