国产av日韩一区二区三区精品,成人性爱视频在线观看,国产,欧美,日韩,一区,www.成色av久久成人,2222eeee成人天堂

Home Java javaTutorial Confusion for Java Beginners: Choice and Application of Collection Framework

Confusion for Java Beginners: Choice and Application of Collection Framework

May 07, 2024 pm 02:09 PM
java collection framework key value pair arrangement

The choice of collection framework depends on data type, access mode and concurrency. List (such as ArrayList) is suitable for storing objects and fast index access; Set (such as HashSet) is suitable for storing unique values; Map (such as HashMap) is suitable for storing key-value pairs and quickly finding values ??according to the key; Queue (such as ArrayDeque) is suitable for storing values ??by key. Data is stored in first-in-first-out order. Specific application scenarios include managing contacts: use ArrayList to store contacts and quickly index names; use HashSet to check whether a contact exists; use HashMap to quickly retrieve contacts based on names.

Confusion for Java Beginners: Choice and Application of Collection Framework

Java beginners’ doubts: the choice and application of collection frameworks

As a Java beginner, choose the correct collection framework It's a puzzling thing. There are many different collection types, each with its own pros and cons. The following are some common collection types and their usage scenarios:

List:

  • Used to store data arranged in order
  • Provide fast index access to elements
  • For example, ArrayList, LinkedList

#Set:

  • is used to store unique Elements of
  • do not provide index access
  • For example, HashSet, TreeSet

Map:

  • use To store key-value pairs
  • Allows fast lookup of values ??based on keys
  • For example, HashMap, TreeMap

Queue:

  • Used to store data arranged in first-in, first-out (FIFO) order
  • For example, ArrayDeque, PriorityQueue

Criteria for selecting collection types:

  • Data type: Consider the type of data you want to store. For example, List is great for storing objects, while Set is great for storing unique values.
  • Access mode: Consider how to access the data. For example, if you need fast index access, you can use a List.
  • Concurrency: Consider whether the data needs to be accessed in a concurrent environment. For example, ConcurrentHashMap is a thread-safe Map implementation.

Practical case:

Suppose you are creating a contact management application. You need to store the contact's name, email, and phone number. Here is an example of implementing this application using different collection types:

Using ArrayList:

import java.util.ArrayList;

public class ContactManager {

    private List<Contact> contacts = new ArrayList<>();

    public void addContact(Contact contact) {
        contacts.add(contact);
    }

    public Contact getContactByName(String name) {
        for (Contact contact : contacts) {
            if (contact.getName().equals(name)) {
                return contact;
            }
        }
        return null;
    }
}

Using HashSet:

import java.util.HashSet;

public class ContactManager {

    private Set<Contact> contacts = new HashSet<>();

    public void addContact(Contact contact) {
        contacts.add(contact);
    }

    public boolean hasContact(Contact contact) {
        return contacts.contains(contact);
    }
}

Using HashMap:

import java.util.HashMap;

public class ContactManager {

    private Map<String, Contact> contacts = new HashMap<>();

    public void addContact(Contact contact) {
        contacts.put(contact.getName(), contact);
    }

    public Contact getContactByName(String name) {
        return contacts.get(name);
    }
}

Which collection type is best for your specific application depends on your specific needs. By understanding the advantages and disadvantages of different collection types, you can choose the type that best meets your requirements.

The above is the detailed content of Confusion for Java Beginners: Choice and Application of Collection Framework. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undress AI Tool

Undress AI Tool

Undress images for free

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Hot Topics

PHP Tutorial
1502
276
How to handle transactions in Java with JDBC? How to handle transactions in Java with JDBC? Aug 02, 2025 pm 12:29 PM

To correctly handle JDBC transactions, you must first turn off the automatic commit mode, then perform multiple operations, and finally commit or rollback according to the results; 1. Call conn.setAutoCommit(false) to start the transaction; 2. Execute multiple SQL operations, such as INSERT and UPDATE; 3. Call conn.commit() if all operations are successful, and call conn.rollback() if an exception occurs to ensure data consistency; at the same time, try-with-resources should be used to manage resources, properly handle exceptions and close connections to avoid connection leakage; in addition, it is recommended to use connection pools and set save points to achieve partial rollback, and keep transactions as short as possible to improve performance.

How to work with Calendar in Java? How to work with Calendar in Java? Aug 02, 2025 am 02:38 AM

Use classes in the java.time package to replace the old Date and Calendar classes; 2. Get the current date and time through LocalDate, LocalDateTime and LocalTime; 3. Create a specific date and time using the of() method; 4. Use the plus/minus method to immutably increase and decrease the time; 5. Use ZonedDateTime and ZoneId to process the time zone; 6. Format and parse date strings through DateTimeFormatter; 7. Use Instant to be compatible with the old date types when necessary; date processing in modern Java should give priority to using java.timeAPI, which provides clear, immutable and linear

Comparing Java Frameworks: Spring Boot vs Quarkus vs Micronaut Comparing Java Frameworks: Spring Boot vs Quarkus vs Micronaut Aug 04, 2025 pm 12:48 PM

Pre-formanceTartuptimeMoryusage, Quarkusandmicronautleadduetocompile-Timeprocessingandgraalvsupport, Withquarkusoftenperforminglightbetterine ServerLess scenarios.2.Thyvelopecosyste,

Understanding Network Ports and Firewalls Understanding Network Ports and Firewalls Aug 01, 2025 am 06:40 AM

Networkportsandfirewallsworktogethertoenablecommunicationwhileensuringsecurity.1.Networkportsarevirtualendpointsnumbered0–65535,withwell-knownportslike80(HTTP),443(HTTPS),22(SSH),and25(SMTP)identifyingspecificservices.2.PortsoperateoverTCP(reliable,c

How does garbage collection work in Java? How does garbage collection work in Java? Aug 02, 2025 pm 01:55 PM

Java's garbage collection (GC) is a mechanism that automatically manages memory, which reduces the risk of memory leakage by reclaiming unreachable objects. 1.GC judges the accessibility of the object from the root object (such as stack variables, active threads, static fields, etc.), and unreachable objects are marked as garbage. 2. Based on the mark-clearing algorithm, mark all reachable objects and clear unmarked objects. 3. Adopt a generational collection strategy: the new generation (Eden, S0, S1) frequently executes MinorGC; the elderly performs less but takes longer to perform MajorGC; Metaspace stores class metadata. 4. JVM provides a variety of GC devices: SerialGC is suitable for small applications; ParallelGC improves throughput; CMS reduces

Using HTML `input` Types for User Data Using HTML `input` Types for User Data Aug 03, 2025 am 11:07 AM

Choosing the right HTMLinput type can improve data accuracy, enhance user experience, and improve usability. 1. Select the corresponding input types according to the data type, such as text, email, tel, number and date, which can automatically checksum and adapt to the keyboard; 2. Use HTML5 to add new types such as url, color, range and search, which can provide a more intuitive interaction method; 3. Use placeholder and required attributes to improve the efficiency and accuracy of form filling, but it should be noted that placeholder cannot replace label.

go by example http middleware logging example go by example http middleware logging example Aug 03, 2025 am 11:35 AM

HTTP log middleware in Go can record request methods, paths, client IP and time-consuming. 1. Use http.HandlerFunc to wrap the processor, 2. Record the start time and end time before and after calling next.ServeHTTP, 3. Get the real client IP through r.RemoteAddr and X-Forwarded-For headers, 4. Use log.Printf to output request logs, 5. Apply the middleware to ServeMux to implement global logging. The complete sample code has been verified to run and is suitable for starting a small and medium-sized project. The extension suggestions include capturing status codes, supporting JSON logs and request ID tracking.

Comparing Java Build Tools: Maven vs. Gradle Comparing Java Build Tools: Maven vs. Gradle Aug 03, 2025 pm 01:36 PM

Gradleisthebetterchoiceformostnewprojectsduetoitssuperiorflexibility,performance,andmoderntoolingsupport.1.Gradle’sGroovy/KotlinDSLismoreconciseandexpressivethanMaven’sverboseXML.2.GradleoutperformsMaveninbuildspeedwithincrementalcompilation,buildcac

See all articles