目錄
用途
策略模式是一種
行為型模式。
結構
圖-策略模式結構圖
Strategy : 定義所有算法的公共接口(AlgorithmInterface)。Context 使用這個接口去調用 ConcreteStrategy 定義的具體算法。
abstract class Strategy {
public abstract void AlgorithmInterface();
}
public abstract void AlgorithmInterface();
}
ConcreteStrategy : 實現 Strategy 中的算法接口(AlgorithmInterface)。
class ConcreteStrategyA extends Strategy {
@Override
public void AlgorithmInterface() {
System.out.println("算法A");
}
}
class ConcreteStrategyB extends Strategy {
@Override
public void AlgorithmInterface() {
System.out.println("算法B");
}
}
class ConcreteStrategyC extends Strategy {
@Override
public void AlgorithmInterface() {
System.out.println("算法C");
}
}
@Override
public void AlgorithmInterface() {
System.out.println("算法A");
}
}
class ConcreteStrategyB extends Strategy {
@Override
public void AlgorithmInterface() {
System.out.println("算法B");
}
}
class ConcreteStrategyC extends Strategy {
@Override
public void AlgorithmInterface() {
System.out.println("算法C");
}
}
Context : 用一個 ConcreteStrategy 來配置。維護一個對 Strategy 對象的引用。
class Context {
Strategy strategy;
public Context(Strategy strategy) {
this.strategy = strategy;
}
public void ContextInterface() {
strategy.AlgorithmInterface();
}
}
Strategy strategy;
public Context(Strategy strategy) {
this.strategy = strategy;
}
public void ContextInterface() {
strategy.AlgorithmInterface();
}
}
測試代碼
public class StrategyPattern {
public static void main(String[] args) {
Context context1 = new Context(new ConcreteStrategyA());
context1.ContextInterface();
Context context2 = new Context(new ConcreteStrategyB());
context2.ContextInterface();
Context context3 = new Context(new ConcreteStrategyC());
context3.ContextInterface();
}
}
public static void main(String[] args) {
Context context1 = new Context(new ConcreteStrategyA());
context1.ContextInterface();
Context context2 = new Context(new ConcreteStrategyB());
context2.ContextInterface();
Context context3 = new Context(new ConcreteStrategyC());
context3.ContextInterface();
}
}
運行結果
算法A
算法B
算法C
算法B
算法C
