Strategy_Pattern

The "Strategy_Pattern" composites the interface object so as to invoke  the different subclasses which implement that interface in an easy manner.

The specific implementation is as follows:

package strategy_pattern;

public interface Strategy {
    public abstract void AlgorithmInterface();
}

package strategy_pattern;

public class ConcreteStrategyA implements Strategy {
    public void AlgorithmInterface() {
        System.out.println("The algorithm A is running!");
    }
}

package strategy_pattern;

public class ConcreteStrategyB implements Strategy {
    public void AlgorithmInterface() {
        System.out.println("The algorithm B is running!");
    }
}

package strategy_pattern;

public class Context {
    Strategy strategy;

    public Context() {
        this.strategy = null;
    }

    public Context(Strategy strategy) {
        this.strategy = strategy;
    }

    public void ContextInterfece() {
        strategy.AlgorithmInterface();// dynamic binding.
    }

    // combine the simple factory pattern.
    public void setStrategy(String type) {
        switch (type) {
        case "A":
            strategy = new ConcreteStrategyA();
            break;
        case "B":
            strategy = new ConcreteStrategyB();
            break;
        default:
            break;
        }
    }

}
package strategy_pattern;

public class Main {
    public static void main(String args[]) {
        Context c = new Context();
        c.setStrategy("A");
        c.ContextInterfece();
        c.setStrategy("B");
        c.ContextInterfece();
    }
}

This is a general introduction to the 23 design patterns：
https://blog.youkuaiyun.com/GZHarryAnonymous/article/details/81567214