The strategy mode is a behavior mode, whose characteristic is that the execution process is fixed, but there are some differences in the intermediate steps; it is determined when it is running. The official meaning is to define a series of algorithms, encapsulate them one by one, and make them interchangeable. Let's use the exhaustive method to give several simple understanding examples:

1. Zhuge Liang's brilliant plan, each of which is a strategy

2. For the travel mode, choose to ride a bicycle or take a car. Each travel mode is a strategy.  

3. Encapsulation of fixed algorithm, etc.

4. Choose payment method for online shopping.

Scenario: when processing data according to the user's needs, you need to choose algorithms. Some fixed algorithms can be expanded.

Here is a code to select the payment method for demonstration:

package pattern.strategy.pay.payport;
import pattern.strategy.pay.PayState;
/**
 * Payment channel
 */
public interface Payment {
   public  PayState pay(String uid,double amount);
}

package pattern.strategy.pay.payport;
public enum  PayType {
    ALI_PAY(new AliPay()),
    WECHAT_PAY(new WechatPay()),
    UNION_PAY(new UnionPay()),
    JD_PAY(new JDPay());
    private Payment payment;

    PayType(Payment payment){
       this.payment=payment;
    }

    public Payment get(){
        return this.payment;
    }
}

package pattern.strategy.pay.payport;
import pattern.strategy.pay.PayState;
public class AliPay implements Payment {
    @Override
    public PayState pay(String uid, double amount) {
        System.out.println("Welcome to Alipay");
        System.out.println("Query account balance,Start deduction");
        return new PayState(200,"Payment successful",amount);
    }
}

package pattern.strategy.pay.payport;
import pattern.strategy.pay.PayState;
public class JDPay implements Payment {
    @Override
    public PayState pay(String uid, double amount) {
        System.out.println("Welcome to JD payment");
        System.out.println("Query account balance,Start deduction");
        return new PayState(200,"Payment successful",amount);
    }
}

package pattern.strategy.pay.payport;
import pattern.strategy.pay.PayState;
public class UnionPay implements Payment {
    @Override
    public PayState pay(String uid, double amount) {
        System.out.println("Welcome to UnionPay payment");
        System.out.println("Query account balance,Start deduction");
        return new PayState(200,"Payment successful",amount);
    }
}

package pattern.strategy.pay.payport;
import pattern.strategy.pay.PayState;
public class WechatPay implements Payment {
    @Override
    public PayState pay(String uid, double amount) {
        System.out.println("Welcome to wechat payment");
        System.out.println("Query account balance,Start deduction");
        return new PayState(200,"Payment successful",amount);
    }
}

package pattern.strategy.pay;
import pattern.strategy.pay.payport.PayType;
public class Order {
    private String uid;
    private String orderId;
    private double amount;

    public Order(String uid,String orderId,double amount){
       this.uid=uid;
       this.orderId=orderId;
       this.amount=amount;
    }

    public PayState pay(PayType payType){
       return payType.get().pay(this.uid,this.amount);
    }

}

package pattern.strategy.pay;

public class PayState {

    private int code;
    private Object data;
    private String msg;

    public PayState(int code,String msg,Object data){
        this.code=code;
        this.msg=msg;
        this.data=data;
    }

    public String toString() {
        return ("Payment status:["+code+"],"+msg+",transaction details :"+data);
    }
}

package pattern.strategy;
import pattern.strategy.pay.Order;
import pattern.strategy.pay.payport.PayType;
public class StrategyTest {
    public static void main(String[] args) {
        Order order=new Order("1","22233333",320);
        System.out.println(order.pay(PayType.ALI_PAY));
    }
}

Test results:

Welcome to Alipay
 Query account balance and start deduction
 Payment status: [200], payment succeeded, transaction details: 320.0