定義一個策略介面:

public interface Strategy {

    void travel();
}

寫兩個實現類:

public class WalkStrategy implements Strategy {
    @Override
public void travel() {
        //walk
}
}

public class PlaneStrategy implements Strategy {
    @Override
public void travel() {
        //plane
}
}

自定義持有策略引用類:

public class StrategyContext {

    private 
 
Strategy strategy;
    public Strategy getStrategy() {
        return strategy;
}

    public void setStrategy(Strategy strategy) {
        this.strategy = strategy;
}

    public void travel() {
        if (strategy != null)
            strategy.travel();
}
}

StrategyContext strategyContext = new StrategyContext();
 
strategyContext.setStrategy(new WalkStrategy());
strategyContext.travel();
strategyContext.setStrategy(new PlaneStrategy());
strategyContext.travel();