策略模式+Enum

策略接口

public interface Strategy {
    int calc(int a, int b);
}

Context，传入不同的策略，完成不同实现

public class Context {

    private Strategy strategy;

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

    public int work(int a, int b) {
        return strategy.calc(a, b);
    }

}

枚举类，枚举不同的策略

public enum Algorithm {
    
    ADD("1", "相加") {
        @Override
        Strategy getStrategy() {
            return new StrategyAdd();
        }
    },
    
    X("2", "相乘") {
        @Override
        Strategy getStrategy() {
            return new StrategyX();
        }
    };

    private String value;
    private String describe;

    Algorithm(String value, String describe) {
        this.value = value;
        this.describe = describe;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    public String getDescribe() {
        return describe;
    }

    public void setDescribe(String describe) {
        this.describe = describe;
    }

	//通过value值获取枚举对象
    static Algorithm getByValue(String value) {
        for (Algorithm algorithm : values()) {
            if (algorithm.getValue().equals(value)) {
                return algorithm;
            }
        }
        return null;
    }

    //每个枚举都需实现自己的策略
    abstract Strategy getStrategy();
}

调用

public class Main {
    public static void main(String[] args) {

        System.out.println(new Context(Algorithm.getByValue("1").getStrategy()).work(3, 2));// 2+3=5
        System.out.println(new Context(Algorithm.getByValue("2").getStrategy()).work(3, 2));// 2*3=6

    }
}