1.Basic introduction
1) Composite Pattern, also called Partial Whole Pattern, creates a tree structure of object groups and combines objects into a tree structure to represent "whole- The hierarchical relationship of "part"
2) The combination mode combines objects according to the tree structure to represent the part and the whole hierarchy
3) This type of design pattern belongs to the structural pattern
4) The combination mode enables users to have consistent access to single objects and combined objects, that is: combination allows customers to process individual objects and combined objects in a consistent manner
2. Structure
The combination mode mainly includes three roles:
Abstract root node (Component): defines the common methods and attributes of objects at all levels of the system, and can predefine some default behaviors and attributes
Branch node (Composite): Define the behavior of branch nodes, store child nodes, and combine branch nodes and leaf nodes to form a tree structure
Leaf node (Leaf): Leaf node object, with no branches below it, is the smallest unit for system level traversal
3. Problems solved by the combination mode
1) The combination pattern solves this problem. When the object we want to process can generate a tree structure, and we want to operate on the nodes and leaves on the tree, it can provide a consistent way, regardless of whether it is a node or a leaf.
2) Corresponding schematic diagram
#4. Combination model to solve school department display
1) Application example requirements
Write a program to display the departmental structure of a school: the demand is as follows. To display the school’s departmental composition on one page, a school has multiple colleges, and a college has multiple departments
2) Idea analysis and illustration (class diagram)
package com.zte; public abstract class OrganizationComponent { private String name;// 名字 private String des;// 说明 public String getName() { return name; } public String getDes() { return des; } protected void add(OrganizationComponent organizationComponent) { // 默认实现 throw new UnsupportedOperationException(); } protected void remove(OrganizationComponent organizationComponent) { // 默认实现 throw new UnsupportedOperationException(); } // 构造器 public OrganizationComponent(String name, String des) { this.name = name; this.des = des; } // 方法print,抽象方法 protected abstract void print(); }Composite non-leaf node
package com.zte; import java.util.ArrayList; import java.util.List; // University 就是 Composite,可以管理College public class University extends OrganizationComponent { List<OrganizationComponent> organizationComponentList = new ArrayList<>(); // 构造器 public University(String name, String des) { super(name, des); } //重写add @Override protected void add(OrganizationComponent organizationComponent) { organizationComponentList.add(organizationComponent); } // 重写remove @Override protected void remove(OrganizationComponent organizationComponent) { organizationComponent.remove(organizationComponent); } @Override protected void print() { System.out.println("==========" + getName() + "========="); for (OrganizationComponent organizationComponent : organizationComponentList) { organizationComponent.print(); } } @Override public String getName() { return super.getName(); } @Override public String getDes() { return super.getDes(); } }Composite non-leaf node
package com.zte; import java.util.ArrayList; import java.util.List; public class College extends OrganizationComponent { // list中存放department List<OrganizationComponent> organizationComponentList = new ArrayList<>(); public College(String name, String des) { super(name, des); } //重写add @Override protected void add(OrganizationComponent organizationComponent) { organizationComponentList.add(organizationComponent); } // 重写remove @Override protected void remove(OrganizationComponent organizationComponent) { organizationComponent.remove(organizationComponent); } @Override protected void print() { System.out.println("==========" + getName() + "========="); for (OrganizationComponent organizationComponent : organizationComponentList) { organizationComponent.print(); } } @Override public String getName() { return super.getName(); } @Override public String getDes() { return super.getDes(); } }Leaf leaf node
package com.zte; public class Department extends OrganizationComponent { public Department(String name, String des) { super(name, des); } // add和remove方法就不需要再写了 @Override protected void print() { System.out.println("===========" + getName() + "========="); } @Override public String getName() { return super.getName(); } @Override public String getDes() { return super.getDes(); } }
package com.zte; public class Client { public static void main(String[] args) { // 创建大学 OrganizationComponent university = new University("清华大学", "中国最好的大学"); // 创建学院 OrganizationComponent college1 = new College("计算机学院", "计算机学院"); OrganizationComponent college2 = new College("信息工程学院", "信息工程学院"); // 创建各个学院下面的系 college1.add(new Department("软件工程", "软件工程")); college1.add(new Department("网络工程", "网络工程")); college1.add(new Department("计算机科学与技术", "老牌专业")); college2.add(new Department("通信工程", "通信工程")); college2.add(new Department("信息工程", "信息工程")); // 将学院添加到学校中 university.add(college1); university.add(college2); // 打印大学底下的所有院系 university.print(); // 打印学院底下的所有系 college1.print(); } }5. Precautions and details of the combination mode1) Simplify the client operation, the client The end only needs to face consistent objects without considering the problem of the whole part or node leaves2) It has strong scalability. When we need to modify the combined object, we only need to adjust the internal hierarchical relationship , the client does not need to make any changes3) It is convenient to create complex hierarchical structures. The client does not need to pay attention to the composition details in the combination, and it is easy to add nodes or leaves to create complex tree structures
4) When you need to traverse the organization structure, or the object being processed has a tree structure, it is very suitable to use the combination mode 5) Requires high abstraction, if there are many differences between nodes and leaves, For example, many methods and properties are different, so it is not suitable to use the combination mode
The above is the detailed content of Java design pattern composition pattern example analysis. For more information, please follow other related articles on the PHP Chinese website!

Emerging technologies pose both threats and enhancements to Java's platform independence. 1) Cloud computing and containerization technologies such as Docker enhance Java's platform independence, but need to be optimized to adapt to different cloud environments. 2) WebAssembly compiles Java code through GraalVM, extending its platform independence, but it needs to compete with other languages for performance.

Different JVM implementations can provide platform independence, but their performance is slightly different. 1. OracleHotSpot and OpenJDKJVM perform similarly in platform independence, but OpenJDK may require additional configuration. 2. IBMJ9JVM performs optimization on specific operating systems. 3. GraalVM supports multiple languages and requires additional configuration. 4. AzulZingJVM requires specific platform adjustments.

Platform independence reduces development costs and shortens development time by running the same set of code on multiple operating systems. Specifically, it is manifested as: 1. Reduce development time, only one set of code is required; 2. Reduce maintenance costs and unify the testing process; 3. Quick iteration and team collaboration to simplify the deployment process.

Java'splatformindependencefacilitatescodereusebyallowingbytecodetorunonanyplatformwithaJVM.1)Developerscanwritecodeonceforconsistentbehavioracrossplatforms.2)Maintenanceisreducedascodedoesn'tneedrewriting.3)Librariesandframeworkscanbesharedacrossproj

To solve platform-specific problems in Java applications, you can take the following steps: 1. Use Java's System class to view system properties to understand the running environment. 2. Use the File class or java.nio.file package to process file paths. 3. Load the local library according to operating system conditions. 4. Use VisualVM or JProfiler to optimize cross-platform performance. 5. Ensure that the test environment is consistent with the production environment through Docker containerization. 6. Use GitHubActions to perform automated testing on multiple platforms. These methods help to effectively solve platform-specific problems in Java applications.

The class loader ensures the consistency and compatibility of Java programs on different platforms through unified class file format, dynamic loading, parent delegation model and platform-independent bytecode, and achieves platform independence.

The code generated by the Java compiler is platform-independent, but the code that is ultimately executed is platform-specific. 1. Java source code is compiled into platform-independent bytecode. 2. The JVM converts bytecode into machine code for a specific platform, ensuring cross-platform operation but performance may be different.

Multithreading is important in modern programming because it can improve program responsiveness and resource utilization and handle complex concurrent tasks. JVM ensures the consistency and efficiency of multithreads on different operating systems through thread mapping, scheduling mechanism and synchronization lock mechanism.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

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

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

SublimeText3 English version
Recommended: Win version, supports code prompts!

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.