应该这样做：
interface Strategy { int execute(int a, int b);}enum Math implements Strategy { Add { @Override public int execute(int a, int b) { return a + b; } }, Subtract { @Override public int execute(int a, int b) { return a - b; } }, Multiply { @Override public int execute(int a, int b) { return a * b; } };}这是对策略使用的Wikipedia文章的重新实现
enum。
或更长一点但更清楚的是一种策略模式：
public interface FailureStrategy { void fail (String message);}enum Failure implements FailureStrategy { Ignore { @Override public void fail(String message) { // Do nothing on success. } }, LogToConsole { @Override public void fail(String message) { System.out.println(message); } }, ErrToConsole { @Override public void fail(String message) { System.err.println(message); } }, RingAlarmBells { @Override public void fail(String message) { // Left to the student. } }, SoundTheKlaxon { @Override public void fail(String message) { // Left to the student. } }, EndTheWorld { @Override public void fail(String message) { // Left to the student. } };}public class SomethingLethal { public FailureStrategy onFail = Failure.EndTheWorld;}public class SomethingDangerous { public FailureStrategy onFail = Failure.RingAlarmBells;}public class SomethingBenign { public FailureStrategy onFail = Failure.Ignore;}
