Java 數學函數 實現加減乘除 代理模式 && 裝飾模式

完整代碼

​interface math {

    double result(double x);//計算帶入具體x的返回結果
    math set(double x);//不同計算增加的內容


}

public class project7 {
    public static void main(String[] args) {
        // x  當 x = 3
        System.out.println(new Function().result(3));
        // x+x  當 x = 4
        System.out.println(new Function().addition().result(4));
        // (x+x)*3  當 x = 5
        System.out.println(new Function().addition().multiplication(3).result(5));

    }
}

//函數
class Function {
    private math function;
    double x;

    public double result(double x) {//帶入值計算返回結果
        this.x = x;
        return function.result(x);
    }
    //創建函數
    public Function() {
        this.function = new Subject();
    }

    //傳參的位常數 不傳參的是自變量

    //加法
    public Function addition(double x) {
        function = new addition(function).set(x);
        return this;
    }
    public Function addition() {
        function = new addition(function).Add();
        return this;
    }

    //乘法
    public Function multiplication(double x) {
        function = new multiplication(function).set(x);
        return this;
    }
    public Function multiplication() {
        function = new multiplication(function).Add();
        return this;
    }

    //減法
    public Function subtraction (double x) {
        function = new subtraction(function).set(x);
        return this;
    }
    public Function subtraction () {
        function = new subtraction(function).Add();
        return this;
    }

    //除法
    public Function division(double x) {
        function = new division(function).set(x);
        return this;
    }
    public Function division() {
        function = new division(function).Add();
        return this;
    }


}

class Subject implements math {
    math target,X = null;
    double x;

    public Subject() { }

    public double result(double x) {
        return x;
    }

    public Subject(math target) {
        this.target = target;
    }

    public math set(double x) {
        this.x = x;
        return this;
    }


    private double R(double x) {
        return X.result(x);
    }

    //增加新變量
    public math Add(){
        X = new Subject();
        return this;
    }

}

class addition extends Subject {

    public addition(math target) {
        super(target);
    }

    public double result(double x) {
        return target.result(x) + ( X == null ? this.x : X.result(x) );
    }



}

class subtraction extends Subject {

    public subtraction(math target) {
        super(target);
    }

    public double result(double x) {
        return target.result(x) - ( X == null ? this.x : X.result(x) );
    }
}

class multiplication extends Subject {

    public multiplication(math target) {
        super(target);
    }

    public double result(double x) {
        return target.result(x) * ( X == null ? this.x : X.result(x) );
    }
}

class division extends Subject {

    public division(math target) {
        super(target);
    }

    public double result(double x) {
        return target.result(x) / ( X == null ? this.x : X.result(x) );
    }
}​

解釋

math 抽象組件

Subject 抽象裝飾類 (真實角色)

成員變量target是一定存在的,X是後添加的函數可有可無

具體裝飾類

加減乘除爲具體的裝飾類
X == null ? this.x : X.result(x)

這個意思是判斷有沒有增加自變量,如果add的是自變量就讓參數和X關聯
如果添加的不是自變量add的就是常數,跟參數無關

Function 代理角色

具體函數
有點小毛病就是不能實現類似於

$\frac{6x}{3x+2}$

上下都是函數的

需要建立兩個分子代理和分母代理才能間接實現