在編寫一個計算器程序時，可以將業務邏輯和顯示分離，業務邏輯封裝為一個類（封裝）；如果要新添加一種運算，可以先創建一個Operation的基類，然後各種運算從Operation類繼承，並實現GetResult()虛函數，這時添加新的運算只需要派生一個新的類，即不需要之前的運算參與編譯。如何讓計算器知道我是希望使用哪種運算呢？應該考慮單獨的類來做這個創造實例的過程，這就是工廠。創建一個OperationFactory類，傳入參數，函數createOperate就可以實例化出合適的對象。
Java代碼如下：
public class OperationFactory { public static abstract class Operation { private double _numberA = 0; private double _numberB = 0; public double get_numberA() { return _numberA; } public void set_numberA(double _numberA) { this._numberA = _numberA; } public double get_numberB() { return _numberB; } public void set_numberB(double _numberB) { this._numberB = _numberB; } abstract double GetResult(); // TODO Auto-generated constructor stub } public static class OperationAdd extends Operation { double GetResult() { double result = get_numberA() + get_numberB(); return result; } } public static class OperationSub extends Operation { double GetResult() { double result = get_numberA() - get_numberB(); return result; } } public static Operation createOperate(String operate){ Operation oper = null; if (operate.equals("+")) { oper = new OperationAdd(); } else if (operate.equals("-")) { oper = new OperationSub(); } return oper; } public static void main(String[] args) { Operation oper; oper = OperationFactory.createOperate("+"); oper.set_numberA(1); oper.set_numberB(2); double result = oper.GetResult(); }}以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持武林網。