23种设计模式第二部分结构模式（6）组合模式

女爷i 2022-07-16 23:51 131阅读 0赞

![57a92d42-4d84-3aa9-a8b9-63a0b02c2c36.jpg][]

## 理解 ##

组合模式有时又叫部分-整体模式在处理类似树形结构的问题时比较方便。

![09cab656-5ff9-380e-9df1-326339ac3509.jpg][]

## 实现 ##

import java.util.Enumeration;
    import java.util.Vector;
    
    public class TreeNode {
    	private String name;
    	private TreeNode parent;
    	private Vector<TreeNode> children = new Vector<TreeNode>();
    	public TreeNode(String name){
    		this.name = name;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public TreeNode getParent() {
    		return parent;
    	}
    	public void setParent(TreeNode parent) {
    		this.parent = parent;
    	}
    	public void add(TreeNode node){
    		children.add(node);
    	}
    	public void remove(TreeNode node){
    		children.remove(node);
    	}
    	public Enumeration<TreeNode> getChildren(){
    		return children.elements();
    	}
    }

public class Tree {
    	TreeNode root = null;
    	public Tree(String name){
    		root = new TreeNode(name);
    	}
    	public static void main(String[] args){
    		Tree tree = new Tree("A");
    		TreeNode nodeB = new TreeNode("B");
    		TreeNode nodeC = new TreeNode("C");
    		
    		nodeB.add(nodeC);
    		tree.root.add(nodeB);
    		System.out.println("build the tree");
    	}
    }

使用场景：将多个对象组合在一起进行操作，常用于表示树形结构中，例如二叉树，数等。

## 维基百科 ##

The composite pattern is a partitioning design pattern. The composite pattern describes that a group of objects is to be treated in the same wayas a single instance of an object.

![600px-Composite_UML_class_diagram_28fixed_29.svg.png][]

=== Java ===
    <source lang=java>
    /** "Component" */
    interface Graphic {
    
        //Prints the graphic.
        public void print();
    }
    
    /** "Composite" */
    import java.util.List;
    import java.util.ArrayList;
    class CompositeGraphic implements Graphic {
    
        //Collection of child graphics.
        private List<Graphic> childGraphics = new ArrayList<Graphic>();
    
        //Prints the graphic.
        public void print() {
            for (Graphic graphic : childGraphics) {
                graphic.print();
            }
        }
    
        //Adds the graphic to the composition.
        public void add(Graphic graphic) {
            childGraphics.add(graphic);
        }
    
        //Removes the graphic from the composition.
        public void remove(Graphic graphic) {
            childGraphics.remove(graphic);
        }
    }
    
    /** "Leaf" */
    class Ellipse implements Graphic {
    
        //Prints the graphic.
        public void print() {
            System.out.println("Ellipse");
        }
    }
    
    /** Client */
    public class Program {
    
        public static void main(String[] args) {
            //Initialize four ellipses
            Ellipse ellipse1 = new Ellipse();
            Ellipse ellipse2 = new Ellipse();
            Ellipse ellipse3 = new Ellipse();
            Ellipse ellipse4 = new Ellipse();
    
            //Initialize three composite graphics
            CompositeGraphic graphic = new CompositeGraphic();
            CompositeGraphic graphic1 = new CompositeGraphic();
            CompositeGraphic graphic2 = new CompositeGraphic();
    
            //Composes the graphics
            graphic1.add(ellipse1);
            graphic1.add(ellipse2);
            graphic1.add(ellipse3);
    
            graphic2.add(ellipse4);
    
            graphic.add(graphic1);
            graphic.add(graphic2);
    
            //Prints the complete graphic (four times the string "Ellipse").
            graphic.print();
        }
    }
    
    </source><span style="color:#3333ff;">
    </span>

[57a92d42-4d84-3aa9-a8b9-63a0b02c2c36.jpg]: /images/20220717/45bd6d982ba04ae1b2037f8b06018f2c.png
[09cab656-5ff9-380e-9df1-326339ac3509.jpg]: /images/20220717/8f458f8c3bb74f088c3d02fabe4d6c24.png
[600px-Composite_UML_class_diagram_28fixed_29.svg.png]: https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Composite_UML_class_diagram_%28fixed%29.svg/600px-Composite_UML_class_diagram_%28fixed%29.svg.png