How Do Java\'s `wait()` and `notify()` Methods Implement a Blocking Queue?
Nov 23, 2024 am 05:56 AM
wait() and notify() in Java: A Simple Scenario with Queue
In Java, the wait() and notify() methods provide a mechanism for thread synchronization. Let's explore a simple scenario where these methods can be used to implement a blocking queue.
Blocking Queue Implementation
A blocking queue is a queue data structure that blocks threads when trying to perform certain operations if specific conditions are not met. In our implementation, we will implement the put() and take() methods, which will block if the queue is full or empty, respectively.
public class BlockingQueue<T> {
private Queue<T> queue = new LinkedList<>();
private int capacity;
public BlockingQueue(int capacity) {
this.capacity = capacity;
}
// Blocks if the queue is full (no space to insert)
public synchronized void put(T element) throws InterruptedException {
while (queue.size() == capacity) {
wait();
}
queue.add(element);
notifyAll();
}
// Blocks if the queue is empty (nothing to remove)
public synchronized T take() throws InterruptedException {
while (queue.isEmpty()) {
wait();
}
T item = queue.remove();
notifyAll();
return item;
}
}
Usage
Now, let's see how to use this blocking queue.
BlockingQueue<Integer> queue = new BlockingQueue<>(10);
// Producer thread: adds elements to the queue
new Thread(() -> {
for (int i = 0; i < 15; i++) {
try {
queue.put(i);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
// Consumer thread: retrieves elements from the queue
new Thread(() -> {
for (int i = 0; i < 15; i++) {
try {
System.out.println(queue.take());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
In this example, the producer thread will add elements to the queue, blocking when it reaches the capacity limit. The consumer thread will retrieve elements, blocking when the queue is empty.
Key Considerations
- Use synchronized blocks: wait() and notify() must be used within synchronized blocks to ensure thread safety and prevent missed signals.
- Use a while loop: Use a while loop to check conditions because of spurious wake-ups (when a thread is re-activated without being notified).
- Consider Java 1.5 concurrency library: Java 1.5 introduced a concurrency library with higher-level abstractions (e.g., Lock and Condition). It offers a cleaner and more versatile approach.
The above is the detailed content of How Do Java\'s `wait()` and `notify()` Methods Implement a Blocking Queue?. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
Difference between HashMap and Hashtable?
Jun 24, 2025 pm 09:41 PM
The difference between HashMap and Hashtable is mainly reflected in thread safety, null value support and performance. 1. In terms of thread safety, Hashtable is thread-safe, and its methods are mostly synchronous methods, while HashMap does not perform synchronization processing, which is not thread-safe; 2. In terms of null value support, HashMap allows one null key and multiple null values, while Hashtable does not allow null keys or values, otherwise a NullPointerException will be thrown; 3. In terms of performance, HashMap is more efficient because there is no synchronization mechanism, and Hashtable has a low locking performance for each operation. It is recommended to use ConcurrentHashMap instead.
Why do we need wrapper classes?
Jun 28, 2025 am 01:01 AM
Java uses wrapper classes because basic data types cannot directly participate in object-oriented operations, and object forms are often required in actual needs; 1. Collection classes can only store objects, such as Lists use automatic boxing to store numerical values; 2. Generics do not support basic types, and packaging classes must be used as type parameters; 3. Packaging classes can represent null values ??to distinguish unset or missing data; 4. Packaging classes provide practical methods such as string conversion to facilitate data parsing and processing, so in scenarios where these characteristics are needed, packaging classes are indispensable.
What are static methods in interfaces?
Jun 24, 2025 pm 10:57 PM
StaticmethodsininterfaceswereintroducedinJava8toallowutilityfunctionswithintheinterfaceitself.BeforeJava8,suchfunctionsrequiredseparatehelperclasses,leadingtodisorganizedcode.Now,staticmethodsprovidethreekeybenefits:1)theyenableutilitymethodsdirectly
How does JIT compiler optimize code?
Jun 24, 2025 pm 10:45 PM
The JIT compiler optimizes code through four methods: method inline, hot spot detection and compilation, type speculation and devirtualization, and redundant operation elimination. 1. Method inline reduces call overhead and inserts frequently called small methods directly into the call; 2. Hot spot detection and high-frequency code execution and centrally optimize it to save resources; 3. Type speculation collects runtime type information to achieve devirtualization calls, improving efficiency; 4. Redundant operations eliminate useless calculations and inspections based on operational data deletion, enhancing performance.
What is an instance initializer block?
Jun 25, 2025 pm 12:21 PM
Instance initialization blocks are used in Java to run initialization logic when creating objects, which are executed before the constructor. It is suitable for scenarios where multiple constructors share initialization code, complex field initialization, or anonymous class initialization scenarios. Unlike static initialization blocks, it is executed every time it is instantiated, while static initialization blocks only run once when the class is loaded.
What is the `final` keyword for variables?
Jun 24, 2025 pm 07:29 PM
InJava,thefinalkeywordpreventsavariable’svaluefrombeingchangedafterassignment,butitsbehaviordiffersforprimitivesandobjectreferences.Forprimitivevariables,finalmakesthevalueconstant,asinfinalintMAX_SPEED=100;wherereassignmentcausesanerror.Forobjectref
What is the Factory pattern?
Jun 24, 2025 pm 11:29 PM
Factory mode is used to encapsulate object creation logic, making the code more flexible, easy to maintain, and loosely coupled. The core answer is: by centrally managing object creation logic, hiding implementation details, and supporting the creation of multiple related objects. The specific description is as follows: the factory mode handes object creation to a special factory class or method for processing, avoiding the use of newClass() directly; it is suitable for scenarios where multiple types of related objects are created, creation logic may change, and implementation details need to be hidden; for example, in the payment processor, Stripe, PayPal and other instances are created through factories; its implementation includes the object returned by the factory class based on input parameters, and all objects realize a common interface; common variants include simple factories, factory methods and abstract factories, which are suitable for different complexities.
What is type casting?
Jun 24, 2025 pm 11:09 PM
There are two types of conversion: implicit and explicit. 1. Implicit conversion occurs automatically, such as converting int to double; 2. Explicit conversion requires manual operation, such as using (int)myDouble. A case where type conversion is required includes processing user input, mathematical operations, or passing different types of values ??between functions. Issues that need to be noted are: turning floating-point numbers into integers will truncate the fractional part, turning large types into small types may lead to data loss, and some languages ??do not allow direct conversion of specific types. A proper understanding of language conversion rules helps avoid errors.
