策略模式（Strategy）
策略模式（Strategy）
我很苦恼啊，UML图没发显示，我添加到附件了定义
策略模式定义了一系列的算法，并将每一个算法封装起来，而且使它们还可以相互替换。策略模式让算法独立于使用它的客户而独立变化。
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策略模式要点：
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UML图
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这个《java设计模式》一书中的图例。
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Context：应用上下文类,持有一个Strategy的对象
Strategy：策略的接口
ConcreteStrategy1,2：接口的实现类（即不同的可以相互替代的算法）
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应用
报表中要使用不同的图案表示同样的数据。
package com.dp;
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//Strategy
public interface DiagramStrategy {
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????? void generateDiagram();
}
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//ConcreteStrategy
public class CuboidDiagramStrategy implements DiagramStrategy {
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????? @Override
????? public void generateDiagram() {
??????????? // TODO Auto-generated method stub
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??????????? System.out.println("输出立方形图形（CuboidDiagramStrategy）");
????? }
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}
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public class CylinderDiagramStrategy implements DiagramStrategy {
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????? @Override
????? public void generateDiagram() {
??????????? // TODO Auto-generated method stub
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??????????? System.out.println("输出圆柱形图形（CylinderDiagram）");
????? }
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}
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//Context应用场景
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public class ReportForm {
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????? //生成报表的策略
????? private DiagramStrategy strategy;
?????
????? public ReportForm(DiagramStrategy strategy) {
??????????? super();
??????????? this.strategy = strategy;
????? }
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????? //产生报表中的图形
????? public void generateDiagram(){
??????????? strategy.generateDiagram();
????? }
?????
?????
????? public DiagramStrategy getStrategy() {
??????????? return strategy;
????? }
????? //设置产生图形的策略
????? public void setStrategy(DiagramStrategy strategy) {
??????????? this.strategy = strategy;
????? }
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}
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在java的api中Comparable和Comparator是Strategy的一个应用。
Package java.uitl;
public interface Comparator<T> {
??? int compare(T o1, T o2);
??? boolean equals(Object obj);
}
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package java.lang;
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public interface Comparable<T> {
??? public int compareTo(T o);
}
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Comparator与Comparable的简单应用
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UML图
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即设计两个接口，Comparable和Comparator，有一个类Cat，它有两个属性Height，Weight，我们可以按照Height或者Weight给他们分辨大小，因此我们可以有两种算法。这样就可以使用Strategy类了。
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/**
?* 按体重比较
?* @author Cody_408516
?*
?*/
public class CatWeightComparator implements Comparator<Cat> {
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????? @Override
????? public int compare(Cat o1, Cat o2) {
??????????? if(o1.getWeight() > o2.getWeight()) return 1;
??????????? else if(o1.getWeight() < o2.getWeight()) return -1;
??????????? return 0;
????? }
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}
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import com.model.Cat;
/**
?* 按身高比较
?* @author Cody_408516
?*
?*/
public class CatHeightComparator implements Comparator<Cat> {
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????? @Override
????? public int compare(Cat o1, Cat o2) {
??????????? if(o1.getHeight()> o2.getHeight()) return 1;
??????????? else if(o1.getHeight() < o2.getHeight()) return -1;
??????????? return 0;
????? }
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}
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public class Cat implements Comparable<Cat> {
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????? //比较器
????? private Comparator<Cat> comparator;
????? //构造器
????? public Cat(float height, float weight) {
??????????? super();
//????????? this.comparator = comparator;
??????????? this.height = height;
??????????? this.weight = weight;
????? }
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????? //猫的属性
????? private float height;
????? private float weight;
?????
????? @Override
????? public int compareTo(Cat o) {
??????????? //返回比较的值
??????????? return comparator.compare(this, o);
????? }
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????? public float getHeight() {
??????????? return height;
????? }
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????? public void setHeight(float height) {
??????????? this.height = height;
????? }
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????? public float getWeight() {
??????????? return weight;
????? }
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????? public void setWeight(float