设计模式之策略Strategy模式 Myth丶恋晨 2022-08-10 14:40 167阅读 0赞 Strategy模式是定义一系列算法,把这些算法定义成一个新的类,在运行的时候动态选择需要的算法。 策略模式的ULM图: 策略模式的例子如下![SouthEast][] 策略模式的例子如下: //文本替换策略 abstract class TextStrategy { protected String text; public TextStrategy(String text) { this.text = text; } public abstract String replace(); } //替换算法1:将文本中"@r@n"替换为"@n" class StrategyOne extends TextStrategy { public StrategyOne(String text) { super(text); } public String replace() { System.out.println(“StrategyOne:”); String result = text.replaceAll("@r@n", "@n")); return result; } } //替换算法2:将文本中"@n"替换为"@r@n" class StrategyTwo extends TextStrategy { public StrategyTwo(String text) { super(text); } public String replace() { System.out.println(“StrategyTwo:”); String result = text.replaceAll(“@n", "@r@n")); return result; } } public class TextCharChange { public static void replace(TextStrategy strategy) { strategy.replace(); } public static void main(String[] args){ String testText1 = "This is a test text!!@n Oh! Line Return!!@n"; String testText2 = This is a test text!!@r@n Oh! Line Return@r@n"; TextCharChange.replace(new StrategyOne(testText2)); TextCharChange.replace(new StrategyTwo(testText1)); } } State模式和Strategy模式很类似,但是又有很明显的区别: 1 State模式设定状态的变化,根据状态的变化来返回相应的处理。 2 Strategy模式是根据需求和场景选择适合的算法。 JDK中策略模式的应用: • java.util.concurrent.ThreadPoolExecutor.AbortPolicy • java.util.concurrent.ThreadPoolExecutor.CallerRunsPolicy • java.util.concurrent.ThreadPoolExecutor.DiscardOldestPolicy • java.util.concurrent.ThreadPoolExecutor.DiscardPolicy • java.util.Comparator [SouthEast]: /images/20220810/9bd1a276f0504f16874ca7006e9d586c.png
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