public interface PriceStrategy {
 int setPrice(int price);
}

public class seventPriceStrategy implements PriceStrategy {
 @Override
 public Double setPrice(int price) {
  return 0.7 * price;
 }
}

public class HalfPriceStrategy implements PriceStrategy {

 @Override
 public Double setPrice(int price) {
 return 0.5 * price;
 }
}

public class PriceAlgorithm {
 private PriceStrategy priceStrategy;


 public PriceStrategy getPriceStrategy() {
 return priceStrategy;
 }

 public void setPriceStrategy(PriceStrategy priceStrategy) {
 this.priceStrategy = priceStrategy;
 }

 public Double getPrice(int price) {
 if(priceStrategy!=null){
  return priceStrategy.setPrice(price);
 }
 return null;
 }
}

 PriceAlgorithm priceAlgorithm = new PriceAlgorithm();
 priceAlgorithm.setPriceStrategy(new HalfPriceStrategy());
 System.out.print("\n" + "1块钱" + "5折后的价格:" + String.valueOf(priceAlgorithm.getPrice(1)));


 PriceAlgorithm priceAlgorithm2 = new PriceAlgorithm();
 priceAlgorithm2.setPriceStrategy(new seventPriceStrategy());
 System.out.print("\n" + "2块钱" + "7折后的价格:" + String.valueOf(priceAlgorithm2.getPrice(2)));