之前寫過一個簡單工廠模式的計算器，現在使用工廠模式來實現一下，區別在於工廠模式將工廠類使用多型的方式來實現，工廠類是介面，多個工廠類來實現這個介面，每個工廠類又只能產出一種物件。這樣的好處是實現了開放-封閉原則，即對擴充套件開放，對修改封閉。此處我還有一個疑問就是：選擇哪個工廠類這個任務怎麼來完成？ 還不是要通過一個判斷，難道在客戶端完成？求解! 如果我有答案會在本文後面以留言的形式加上。

package tom.java.com; import java.util.Scanner; public class Cal2 { public static void main(String[] args) throws Exception { IO io = new IO(); Calculate2 calculate2 = CalFactory2.createCal(io.getNum(), io.getFh()); System.out.println("The Answer is " + calculate2.Cal()); } } class IO2 { private long[] num; private String fh; public IO2 (){ num = new long[2]; fh = null; Scanner scan = new Scanner(System.in); System.out.println("Please input the first number:"); if (scan.hasNextInt()) num[0] = scan.nextInt(); System.out.println("Please input the second number:"); if (scan.hasNextInt()) num[1] = scan.nextInt(); System.out.println("Please input the Cal method:"); if (scan.hasNext()) fh = scan.next(); } public void outputData () { System.out.println("the first number is = " + num[0]); System.out.println("the second number is = " + num[1]); System.out.println("the Cal method is = " + fh); } public long[] getNum () { return num; } public String getFh () { return fh; } } abstract class Calculate2 { private long[] num; public Calculate2(long[] numNew) { num = numNew; } public long[] getNum () { return num; } public abstract long Cal(); } class AddCal2 extends Calculate2 { public AddCal2(long[] numNew) { super(numNew); // TODO Auto-generated constructor stub } @Override public long Cal() { // TODO Auto-generated method stub long num[] = super.getNum(); return num[0] + num[1]; } } class SubCal2 extends Calculate2 { public SubCal2(long[] numNew) { super(numNew); // TODO Auto-generated constructor stub } @Override public long Cal() { // TODO Auto-generated method stub long num[] = super.getNum(); return num[0] - num[1]; } } class MulCal2 extends Calculate2 { public MulCal2(long[] numNew) { super(numNew); // TODO Auto-generated constructor stub } @Override public long Cal() { // TODO Auto-generated method stub long num[] = super.getNum(); return num[0] * num[1]; } } class DivCal2 extends Calculate2 { public DivCal2(long[] numNew) { super(numNew); // TODO Auto-generated constructor stub } @Override public long Cal() { // TODO Auto-generated method stub long num[] = super.getNum(); if (num[1] == 0) { System.out.println("The Second Num Could not be 0"); } return num[0] / num[1]; } } interface CalFactoryInt{ public Calculate2 createCal(long[] num); } class AddFactory implements CalFactoryInt{ private static long[] num; @Override public Calculate2 createCal(long[] num) { // TODO Auto-generated method stub return new AddCal2(num); } } class SubFactory implements CalFactoryInt{ private static long[] num; @Override public Calculate2 createCal(long[] num) { // TODO Auto-generated method stub return new SubCal2(num); } } class DivFactory implements CalFactoryInt{ private static long[] num; @Override public Calculate2 createCal(long[] num) { // TODO Auto-generated method stub return new DivCal2(num); } } class MulFactory implements CalFactoryInt{ private static long[] num; @Override public Calculate2 createCal(long[] num) { // TODO Auto-generated method stub return new MulCal2(num); } } class CalFactory2 { private static long[] num; private static String fh; private static Calculate2 cal; public static Calculate2 createCal(long[] numNew, String fhNew) throws Exception { num = numNew; fh = fhNew; cal = null; switch (fh) { case "+": cal = new AddFactory().createCal(num);break; case "-": cal = new SubFactory().createCal(num);break; case "*": cal = new SubFactory().createCal(num);break; case "/": if (num[1] == 0) { throw new Exception("The Second Num Could not be 0"); }else { cal = new DivFactory().createCal(num); } break; default : System.out.println("Wrong Cal Method"); break; } return cal; } } </textarea >

關於上面我提出的那個問題，我想應該是例子的原因，不知道大家怎麼認為呢？？